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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-21 11:54:28 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-21 11:54:28 +0000 |
| commit | e6918187568dbd01842d8d1d2c808ce16a894239 (patch) | |
| tree | 64f88b554b444a49f656b6c656111a145cbbaa28 /src/boost/tools/auto_index/test/test1.gold | |
| parent | Initial commit. (diff) | |
| download | ceph-upstream/18.2.2.tar.xz ceph-upstream/18.2.2.zip | |
Adding upstream version 18.2.2.upstream/18.2.2
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/boost/tools/auto_index/test/test1.gold')
| -rw-r--r-- | src/boost/tools/auto_index/test/test1.gold | 6671 |
1 files changed, 6671 insertions, 0 deletions
diff --git a/src/boost/tools/auto_index/test/test1.gold b/src/boost/tools/auto_index/test/test1.gold new file mode 100644 index 000000000..ec051ab96 --- /dev/null +++ b/src/boost/tools/auto_index/test/test1.gold @@ -0,0 +1,6671 @@ +<?xml version="1.0"?> +<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> +<!-- + +This file is based upon the type traits docs, but has had additional XML elements added to it +to ensure complete testing. + +--> + +<chapter xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" id="boost_typetraits" rev:last-revision="$Date: 2008-11-28 12:41:45 +0000 (Fri, 28 Nov 2008) $"> + <chapterinfo><author> + <firstname>various</firstname> <surname>authors</surname> + </author><copyright> + <year>2000</year> <year>2006</year> <holder>Adobe Systems Inc, David Abrahams, + Steve Cleary, Beman Dawes, Aleksey Gurtovoy, Howard Hinnant, Jesse Jones, Mat + Marcus, Itay Maman, John Maddock, Alexander Nasonov, Thorsten Ottosen, Robert + Ramey and Jeremy Siek</holder> + </copyright><legalnotice> + <para> + Distributed under the Boost Software License, Version 1.0. (See accompanying + file LICENSE_1_0.txt or copy at <ulink url="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</ulink>) + </para> + </legalnotice></chapterinfo> + <title>Boost.TypeTraits</title> + <para> + A printer-friendly <ulink url="http://svn.boost.org/svn/boost/sandbox/pdf/type_traits/release/type_traits.pdf">PDF + version of this manual is also available</ulink>. + </para> + <section id="boost_typetraits.intro"><indexterm type="test_index_1"><primary>type-traits</primary><secondary>Introduction</secondary></indexterm><indexterm><primary>Introduction</primary><secondary>type-traits</secondary></indexterm><indexterm type="test_index_1"><primary>type-traits</primary><secondary>Introduction</secondary></indexterm><indexterm><primary>Introduction</primary><secondary>type-traits</secondary></indexterm><indexterm type="test_index_1"><primary>type-traits</primary><secondary>Introduction</secondary></indexterm><indexterm><primary>Introduction</primary><secondary>type-traits</secondary></indexterm> + <title><link linkend="boost_typetraits.intro"> Introduction</link></title> + <para> + The Boost type-traits library contains a set of very specific traits classes, + each of which encapsulate a single trait from the C++ type system; for example, + is a type a pointer or a reference type? Or does a type have a trivial constructor, + or a const-qualifier? + </para> + <para> + The type-traits classes share a unified design: each class inherits from a + the type <link linkend="boost_typetraits.reference.integral_constant">true_type</link> + if the type has the specified property and inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link> + otherwise. + </para> + <para> + The type-traits library also contains a set of classes that perform a specific + transformation on a type; for example, they can remove a top-level const or + volatile qualifier from a type. Each class that performs a transformation defines + a single typedef-member <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">type</phrase></computeroutput> + that is the result of the transformation. + </para> + </section> + <section id="boost_typetraits.background"><indexterm type="test_index_2"><primary>type-traits</primary><secondary>Background and Tutorial</secondary></indexterm><indexterm><primary>Background and Tutorial</primary><secondary>type-traits</secondary></indexterm><indexterm type="test_index_2"><primary>type-traits</primary><secondary>Background and Tutorial</secondary></indexterm><indexterm><primary>Background and Tutorial</primary><secondary>type-traits</secondary></indexterm><indexterm type="class_name"><primary>remove_extent</primary><secondary>Background and Tutorial</secondary></indexterm><indexterm><primary>Background and Tutorial</primary><secondary>remove_extent</secondary></indexterm><indexterm type="class_name"><primary>is_pointer</primary><secondary>Background and Tutorial</secondary></indexterm><indexterm><primary>Background and Tutorial</primary><secondary>is_pointer</secondary></indexterm><indexterm type="class_name"><primary>is_void</primary><secondary>Background and Tutorial</secondary></indexterm><indexterm><primary>Background and Tutorial</primary><secondary>is_void</secondary></indexterm><indexterm type="test_index_2"><primary>type-traits</primary><secondary>Background and Tutorial</secondary></indexterm><indexterm><primary>Background and Tutorial</primary><secondary>type-traits</secondary></indexterm><indexterm type="test_index_2"><primary>type-traits</primary><secondary>Background and Tutorial</secondary></indexterm><indexterm><primary>Background and Tutorial</primary><secondary>type-traits</secondary></indexterm><indexterm type="test_index_2"><primary>type-traits</primary><secondary>Background and Tutorial</secondary></indexterm><indexterm><primary>Background and Tutorial</primary><secondary>type-traits</secondary></indexterm> + <title><link linkend="boost_typetraits.background"> Background and Tutorial</link></title> + <para> + The following is an updated version of the article "C++ Type traits" + by John Maddock and Steve Cleary that appeared in the October 2000 issue of + <ulink url="http://www.ddj.com">Dr Dobb's Journal</ulink>. + </para> + <para> + Generic programming (writing code which works with any data type meeting a + set of requirements) has become the method of choice for providing reusable + code. However, there are times in generic programming when "generic" + just isn't good enough - sometimes the differences between types are too large + for an efficient generic implementation. This is when the traits technique + becomes important - by encapsulating those properties that need to be considered + on a type by type basis inside a traits class, we can minimize the amount of + code that has to differ from one type to another, and maximize the amount of + generic code. + </para> + <?dbfo keep-together="auto" ?> + <para> + <indexterm> + <primary>Foo1</primary> + </indexterm> + Consider an example: when working with character strings, one common operation + is to determine the length of a null terminated string. Clearly it's possible + to write generic code that can do this, but it turns out that there are much + more efficient methods available: for example, the C library functions <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">strlen</phrase></computeroutput> and <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">wcslen</phrase></computeroutput> + are usually written in assembler, and with suitable hardware support can be + considerably faster than a generic version written in C++. The authors of the + C++ standard library realized this, and abstracted the properties of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">char</phrase></computeroutput> and <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">wchar_t</phrase></computeroutput> + into the class <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">char_traits</phrase></computeroutput>. + Generic code that works with character strings can simply use <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">char_traits</phrase><phrase role="special"><>::</phrase><phrase role="identifier">length</phrase></computeroutput> to determine the length of a null + terminated string, safe in the knowledge that specializations of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">char_traits</phrase></computeroutput> will use the most appropriate + method available to them. + </para> + <anchor id="boost_typetraits.background.type_traits"/> + <bridgehead renderas="sect4"> + <link linkend="boost_typetraits.background.type_traits">Type Traits</link> + </bridgehead> + <para> + Class <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">char_traits</phrase></computeroutput> is a classic + example of a collection of type specific properties wrapped up in a single + class - what Nathan Myers termed a <emphasis>baggage class</emphasis><link linkend="background.references">[1]</link>. In the Boost type-traits library, + we<link linkend="background.references">[2]</link> have written a set of very + specific traits classes, each of which encapsulate a single trait from the + C++ type system; for example, is a type a pointer or a reference type? Or does + a type have a trivial constructor, or a const-qualifier? The type-traits classes + share a unified design: each class inherits from a the type <link linkend="boost_typetraits.reference.integral_constant">true_type</link> + if the type has the specified property and inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link> + otherwise. As we will show, these classes can be used in generic programming + to determine the properties of a given type and introduce optimizations that + are appropriate for that case. + </para> + <para> + The type-traits library also contains a set of classes that perform a specific + transformation on a type; for example, they can remove a top-level const or + volatile qualifier from a type. Each class that performs a transformation defines + a single typedef-member <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">type</phrase></computeroutput> + that is the result of the transformation. All of the type-traits classes are + defined inside namespace <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">boost</phrase></computeroutput>; + for brevity, namespace-qualification is omitted in most of the code samples + given. + </para> + <anchor id="boost_typetraits.background.implementation"/> + <bridgehead renderas="sect4"> + <link linkend="boost_typetraits.background.implementation">Implementation</link> + </bridgehead> + <para> + There are far too many separate classes contained in the type-traits library + to give a full implementation here - see the source code in the Boost library + for the full details - however, most of the implementation is fairly repetitive + anyway, so here we will just give you a flavor for how some of the classes + are implemented. Beginning with possibly the simplest class in the library, + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_void</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">></phrase></computeroutput> inherits + from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput> + only if <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> is <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">void</phrase></computeroutput>. + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">typename</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_void">is_void</link> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <link linkend="boost_typetraits.reference.integral_constant">false_type</link><phrase role="special">{};</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_void">is_void</link><phrase role="special"><</phrase><phrase role="keyword">void</phrase><phrase role="special">></phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <link linkend="boost_typetraits.reference.integral_constant">true_type</link><phrase role="special">{};</phrase> +</programlisting> + <para> + Here we define a primary version of the template class <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.is_void">is_void</link></computeroutput>, + and provide a full-specialization when <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> + is <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">void</phrase></computeroutput>. While full specialization + of a template class is an important technique, sometimes we need a solution + that is halfway between a fully generic solution, and a full specialization. + This is exactly the situation for which the standards committee defined partial + template-class specialization. As an example, consider the class <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">boost</phrase><phrase role="special">::</phrase><phrase role="identifier">is_pointer</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">></phrase></computeroutput>: + here we needed a primary version that handles all the cases where T is not + a pointer, and a partial specialization to handle all the cases where T is + a pointer: + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">typename</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_pointer">is_pointer</link> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <link linkend="boost_typetraits.reference.integral_constant">false_type</link><phrase role="special">{};</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">typename</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_pointer">is_pointer</link><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">*></phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <link linkend="boost_typetraits.reference.integral_constant">true_type</link><phrase role="special">{};</phrase> +</programlisting> + <para> + The syntax for partial specialization is somewhat arcane and could easily occupy + an article in its own right; like full specialization, in order to write a + partial specialization for a class, you must first declare the primary template. + The partial specialization contains an extra <...> after the class name + that contains the partial specialization parameters; these define the types + that will bind to that partial specialization rather than the default template. + The rules for what can appear in a partial specialization are somewhat convoluted, + but as a rule of thumb if you can legally write two function overloads of the + form: + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">void</phrase> <phrase role="identifier">foo</phrase><phrase role="special">(</phrase><phrase role="identifier">T</phrase><phrase role="special">);</phrase> +<phrase role="keyword">void</phrase> <phrase role="identifier">foo</phrase><phrase role="special">(</phrase><phrase role="identifier">U</phrase><phrase role="special">);</phrase> +</programlisting> + <para> + Then you can also write a partial specialization of the form: + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">typename</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">class</phrase> <phrase role="identifier">c</phrase><phrase role="special">{</phrase> <phrase role="comment">/*details*/</phrase> <phrase role="special">};</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">typename</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">class</phrase> <phrase role="identifier">c</phrase><phrase role="special"><</phrase><phrase role="identifier">U</phrase><phrase role="special">>{</phrase> <phrase role="comment">/*details*/</phrase> <phrase role="special">};</phrase> +</programlisting> + <para> + This rule is by no means foolproof, but it is reasonably simple to remember + and close enough to the actual rule to be useful for everyday use. + </para> + <para> + As a more complex example of partial specialization consider the class <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_extent</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">></phrase></computeroutput>. This + class defines a single typedef-member <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">type</phrase></computeroutput> + that is the same type as T but with any top-level array bounds removed; this + is an example of a traits class that performs a transformation on a type: + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">typename</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.remove_extent">remove_extent</link> +<phrase role="special">{</phrase> <phrase role="keyword">typedef</phrase> <phrase role="identifier">T</phrase> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> <phrase role="special">};</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">typename</phrase> <phrase role="identifier">T</phrase><phrase role="special">,</phrase> <phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase> <phrase role="identifier">N</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.remove_extent">remove_extent</link><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">[</phrase><phrase role="identifier">N</phrase><phrase role="special">]></phrase> +<phrase role="special">{</phrase> <phrase role="keyword">typedef</phrase> <phrase role="identifier">T</phrase> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> <phrase role="special">};</phrase> +</programlisting> + <para> + The aim of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.remove_extent">remove_extent</link></computeroutput> + is this: imagine a generic algorithm that is passed an array type as a template + parameter, <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.remove_extent">remove_extent</link></computeroutput> + provides a means of determining the underlying type of the array. For example + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_extent</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">[</phrase><phrase role="number">4</phrase><phrase role="special">][</phrase><phrase role="number">5</phrase><phrase role="special">]>::</phrase><phrase role="identifier">type</phrase></computeroutput> would evaluate to the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">[</phrase><phrase role="number">5</phrase><phrase role="special">]</phrase></computeroutput>. This example also shows that the number of + template parameters in a partial specialization does not have to match the + number in the default template. However, the number of parameters that appear + after the class name do have to match the number and type of the parameters + in the default template. + </para> + <anchor id="boost_typetraits.background.optimized_copy"/> + <bridgehead renderas="sect4"> + <link linkend="boost_typetraits.background.optimized_copy">Optimized copy</link> + </bridgehead> + <para> + As an example of how the type traits classes can be used, consider the standard + library algorithm copy: + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase><phrase role="special"><</phrase><phrase role="keyword">typename</phrase> <phrase role="identifier">Iter1</phrase><phrase role="special">,</phrase> <phrase role="keyword">typename</phrase> <phrase role="identifier">Iter2</phrase><phrase role="special">></phrase> +<phrase role="identifier">Iter2</phrase> <phrase role="identifier">copy</phrase><phrase role="special">(</phrase><phrase role="identifier">Iter1</phrase> <phrase role="identifier">first</phrase><phrase role="special">,</phrase> <phrase role="identifier">Iter1</phrase> <phrase role="identifier">last</phrase><phrase role="special">,</phrase> <phrase role="identifier">Iter2</phrase> <phrase role="identifier">out</phrase><phrase role="special">);</phrase> +</programlisting> + <para> + Obviously, there's no problem writing a generic version of copy that works + for all iterator types <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">Iter1</phrase></computeroutput> + and <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">Iter2</phrase></computeroutput>; however, there are + some circumstances when the copy operation can best be performed by a call + to <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">memcpy</phrase></computeroutput>. In order to implement + copy in terms of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">memcpy</phrase></computeroutput> all + of the following conditions need to be met: + </para> + <itemizedlist> + <listitem> + Both of the iterator types <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">Iter1</phrase></computeroutput> + and <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">Iter2</phrase></computeroutput> must be pointers. + </listitem> + <listitem> + Both <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">Iter1</phrase></computeroutput> and <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">Iter2</phrase></computeroutput> must point to the same type - excluding + const and volatile-qualifiers. + </listitem> + <listitem> + The type pointed to by <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">Iter1</phrase></computeroutput> + must have a trivial assignment operator. + </listitem> + </itemizedlist> + <para> + By trivial assignment operator we mean that the type is either a scalar type<link linkend="background.references">[3]</link> or: + </para> + <itemizedlist> + <listitem> + The type has no user defined assignment operator. + </listitem> + <listitem> + The type does not have any data members that are references. + </listitem> + <listitem> + All base classes, and all data member objects must have trivial assignment + operators. + </listitem> + </itemizedlist> + <para> + If all these conditions are met then a type can be copied using <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">memcpy</phrase></computeroutput> rather than using a compiler generated + assignment operator. The type-traits library provides a class <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.has_trivial_assign">has_trivial_assign</link></computeroutput>, + such that <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_assign</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is true only if T has a trivial assignment + operator. This class "just works" for scalar types, but has to be + explicitly specialised for class/struct types that also happen to have a trivial + assignment operator. In other words if <link linkend="boost_typetraits.reference.has_trivial_assign">has_trivial_assign</link> + gives the wrong answer, it will give the "safe" wrong answer - that + trivial assignment is not allowable. + </para> + <para> + The code for an optimized version of copy that uses <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">memcpy</phrase></computeroutput> + where appropriate is given in <link linkend="boost_typetraits.examples.copy">the + examples</link>. The code begins by defining a template function <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">do_copy</phrase></computeroutput> that performs a "slow but safe" + copy. The last parameter passed to this function may be either a <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput> + or a <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">false_type</link></computeroutput>. + Following that there is an overload of do<emphasis role="underline">copy that + uses `memcpy`: this time the iterators are required to actually be pointers + to the same type, and the final parameter must be a `</emphasis>_true_type<computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="special">.</phrase> <phrase role="identifier">Finally</phrase><phrase role="special">,</phrase> <phrase role="identifier">the</phrase> <phrase role="identifier">version</phrase> + <phrase role="identifier">of</phrase> </computeroutput>copy<computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="identifier">calls</phrase> + </computeroutput>do<emphasis role="underline">copy`, passing `</emphasis>_has_trivial_assign<value_type>()` + as the final parameter: this will dispatch to the optimized version where appropriate, + otherwise it will call the "slow but safe version". + </para> + <anchor id="boost_typetraits.background.was_it_worth_it_"/> + <bridgehead renderas="sect4"> + <link linkend="boost_typetraits.background.was_it_worth_it_">Was it worth it?</link> + </bridgehead> + <para> + It has often been repeated in these columns that "premature optimization + is the root of all evil" <link linkend="background.references">[4]</link>. + So the question must be asked: was our optimization premature? To put this + in perspective the timings for our version of copy compared a conventional + generic copy<link linkend="background.references">[5]</link> are shown in table + 1. + </para> + <para> + Clearly the optimization makes a difference in this case; but, to be fair, + the timings are loaded to exclude cache miss effects - without this accurate + comparison between algorithms becomes difficult. However, perhaps we can add + a couple of caveats to the premature optimization rule: + </para> + <itemizedlist> + <listitem> + If you use the right algorithm for the job in the first place then optimization + will not be required; in some cases, memcpy is the right algorithm. + </listitem> + <listitem> + If a component is going to be reused in many places by many people then optimizations + may well be worthwhile where they would not be so for a single case - in + other words, the likelihood that the optimization will be absolutely necessary + somewhere, sometime is that much higher. Just as importantly the perceived + value of the stock implementation will be higher: there is no point standardizing + an algorithm if users reject it on the grounds that there are better, more + heavily optimized versions available. + </listitem> + </itemizedlist> + <table frame="all"> <title>Time taken to copy 1000 elements using `copy<const + T*, T*>` (times in micro-seconds)</title> + <tgroup cols="3"> + <thead> + <row> + <entry> + <para> + Version + </para> + </entry><entry> + <para> + T + </para> + </entry><entry> + <para> + Time + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + "Optimized" copy + </para> + </entry><entry> + <para> + char + </para> + </entry><entry> + <para> + 0.99 + </para> + </entry> + </row> + <row> + <entry> + <para> + Conventional copy + </para> + </entry><entry> + <para> + char + </para> + </entry><entry> + <para> + 8.07 + </para> + </entry> + </row> + <row> + <entry> + <para> + "Optimized" copy + </para> + </entry><entry> + <para> + int + </para> + </entry><entry> + <para> + 2.52 + </para> + </entry> + </row> + <row> + <entry> + <para> + Conventional copy + </para> + </entry><entry> + <para> + int + </para> + </entry><entry> + <para> + 8.02 + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> <anchor id="boost_typetraits.background.pair_of_references"/> + <bridgehead renderas="sect4"> + <link linkend="boost_typetraits.background.pair_of_references">Pair of References</link> + </bridgehead> + <para> + The optimized copy example shows how type traits may be used to perform optimization + decisions at compile-time. Another important usage of type traits is to allow + code to compile that otherwise would not do so unless excessive partial specialization + is used. This is possible by delegating partial specialization to the type + traits classes. Our example for this form of usage is a pair that can hold + references <link linkend="background.references">[6]</link>. + </para> + <para> + First, let us examine the definition of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">pair</phrase></computeroutput>, omitting + the comparison operators, default constructor, and template copy constructor + for simplicity: + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">typename</phrase> <phrase role="identifier">T1</phrase><phrase role="special">,</phrase> <phrase role="keyword">typename</phrase> <phrase role="identifier">T2</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">pair</phrase> +<phrase role="special">{</phrase> +<phrase role="keyword">typedef</phrase> <phrase role="identifier">T1</phrase> <phrase role="identifier">first_type</phrase><phrase role="special">;</phrase> +<phrase role="keyword">typedef</phrase> <phrase role="identifier">T2</phrase> <phrase role="identifier">second_type</phrase><phrase role="special">;</phrase> + +<phrase role="identifier">T1</phrase> <phrase role="identifier">first</phrase><phrase role="special">;</phrase> +<phrase role="identifier">T2</phrase> <phrase role="identifier">second</phrase><phrase role="special">;</phrase> + +<phrase role="identifier">pair</phrase><phrase role="special">(</phrase><phrase role="keyword">const</phrase> <phrase role="identifier">T1</phrase> <phrase role="special">&</phrase> <phrase role="identifier">nfirst</phrase><phrase role="special">,</phrase> <phrase role="keyword">const</phrase> <phrase role="identifier">T2</phrase> <phrase role="special">&</phrase> <phrase role="identifier">nsecond</phrase><phrase role="special">)</phrase> +<phrase role="special">:</phrase><phrase role="identifier">first</phrase><phrase role="special">(</phrase><phrase role="identifier">nfirst</phrase><phrase role="special">),</phrase> <phrase role="identifier">second</phrase><phrase role="special">(</phrase><phrase role="identifier">nsecond</phrase><phrase role="special">)</phrase> <phrase role="special">{</phrase> <phrase role="special">}</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + Now, this "pair" cannot hold references as it currently stands, because + the constructor would require taking a reference to a reference, which is currently + illegal <link linkend="background.references">[7]</link>. Let us consider what + the constructor's parameters would have to be in order to allow "pair" + to hold non-reference types, references, and constant references: + </para> + <table frame="all"> <title>Required Constructor Argument Types</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Type of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T1</phrase></computeroutput> + </para> + </entry><entry> + <para> + Type of parameter to initializing constructor + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + T + </para> + </entry><entry> + <para> + const T & + </para> + </entry> + </row> + <row> + <entry> + <para> + T & + </para> + </entry><entry> + <para> + T & + </para> + </entry> + </row> + <row> + <entry> + <para> + const T & + </para> + </entry><entry> + <para> + const T & + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + <para> + A little familiarity with the type traits classes allows us to construct a + single mapping that allows us to determine the type of parameter from the type + of the contained class. The type traits classes provide a transformation <link linkend="boost_typetraits.reference.add_reference">add_reference</link>, which + adds a reference to its type, unless it is already a reference. + </para> + <table frame="all"> <title>Using add_reference to synthesize the correct constructor + type</title> + <tgroup cols="3"> + <thead> + <row> + <entry> + <para> + Type of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T1</phrase></computeroutput> + </para> + </entry><entry> + <para> + Type of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">const</phrase> <phrase role="identifier">T1</phrase></computeroutput> + </para> + </entry><entry> + <para> + Type of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_reference</phrase><phrase role="special"><</phrase><phrase role="keyword">const</phrase> <phrase role="identifier">T1</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + T + </para> + </entry><entry> + <para> + const T + </para> + </entry><entry> + <para> + const T & + </para> + </entry> + </row> + <row> + <entry> + <para> + T & + </para> + </entry><entry> + <para> + T & [8] + </para> + </entry><entry> + <para> + T & + </para> + </entry> + </row> + <row> + <entry> + <para> + const T & + </para> + </entry><entry> + <para> + const T & + </para> + </entry><entry> + <para> + const T & + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + <para> + This allows us to build a primary template definition for <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">pair</phrase></computeroutput> + that can contain non-reference types, reference types, and constant reference + types: + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">typename</phrase> <phrase role="identifier">T1</phrase><phrase role="special">,</phrase> <phrase role="keyword">typename</phrase> <phrase role="identifier">T2</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">pair</phrase> +<phrase role="special">{</phrase> +<phrase role="keyword">typedef</phrase> <phrase role="identifier">T1</phrase> <phrase role="identifier">first_type</phrase><phrase role="special">;</phrase> +<phrase role="keyword">typedef</phrase> <phrase role="identifier">T2</phrase> <phrase role="identifier">second_type</phrase><phrase role="special">;</phrase> + +<phrase role="identifier">T1</phrase> <phrase role="identifier">first</phrase><phrase role="special">;</phrase> +<phrase role="identifier">T2</phrase> <phrase role="identifier">second</phrase><phrase role="special">;</phrase> + +<phrase role="identifier">pair</phrase><phrase role="special">(</phrase><phrase role="identifier">boost</phrase><phrase role="special">::</phrase><link linkend="boost_typetraits.reference.add_reference">add_reference</link><phrase role="special"><</phrase><phrase role="keyword">const</phrase> <phrase role="identifier">T1</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase> <phrase role="identifier">nfirst</phrase><phrase role="special">,</phrase> + <phrase role="identifier">boost</phrase><phrase role="special">::</phrase><link linkend="boost_typetraits.reference.add_reference">add_reference</link><phrase role="special"><</phrase><phrase role="keyword">const</phrase> <phrase role="identifier">T2</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase> <phrase role="identifier">nsecond</phrase><phrase role="special">)</phrase> +<phrase role="special">:</phrase><phrase role="identifier">first</phrase><phrase role="special">(</phrase><phrase role="identifier">nfirst</phrase><phrase role="special">),</phrase> <phrase role="identifier">second</phrase><phrase role="special">(</phrase><phrase role="identifier">nsecond</phrase><phrase role="special">)</phrase> <phrase role="special">{</phrase> <phrase role="special">}</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + Add back in the standard comparison operators, default constructor, and template + copy constructor (which are all the same), and you have a <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">pair</phrase></computeroutput> that + can hold reference types! + </para> + <para> + This same extension could have been done using partial template specialization + of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">pair</phrase></computeroutput>, but to specialize + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">pair</phrase></computeroutput> in this way would require + three partial specializations, plus the primary template. Type traits allows + us to define a single primary template that adjusts itself auto-magically to + any of these partial specializations, instead of a brute-force partial specialization + approach. Using type traits in this fashion allows programmers to delegate + partial specialization to the type traits classes, resulting in code that is + easier to maintain and easier to understand. + </para> + <anchor id="boost_typetraits.background.conclusion"/> + <bridgehead renderas="sect4"> + <link linkend="boost_typetraits.background.conclusion">Conclusion</link> + </bridgehead> + <para> + We hope that in this article we have been able to give you some idea of what + type-traits are all about. A more complete listing of the available classes + are in the boost documentation, along with further examples using type traits. + Templates have enabled C++ uses to take the advantage of the code reuse that + generic programming brings; hopefully this article has shown that generic programming + does not have to sink to the lowest common denominator, and that templates + can be optimal as well as generic. + </para> + <anchor id="boost_typetraits.background.acknowledgements"/> + <bridgehead renderas="sect4"> + <link linkend="boost_typetraits.background.acknowledgements">Acknowledgements</link> + </bridgehead> + <para> + The authors would like to thank Beman Dawes and Howard Hinnant for their helpful + comments when preparing this article. + </para> + <anchor id="background.references"/> <anchor id="boost_typetraits.background.references"/> + <bridgehead renderas="sect4"> + <link linkend="boost_typetraits.background.references">References</link> + </bridgehead> + <orderedlist inheritnum="ignore" continuation="restarts"> + <listitem> + Nathan C. Myers, C++ Report, June 1995. + </listitem> + <listitem> + The type traits library is based upon contributions by Steve Cleary, Beman + Dawes, Howard Hinnant and John Maddock: it can be found at www.boost.org. + </listitem> + <listitem> + A scalar type is an arithmetic type (i.e. a built-in integer or floating + point type), an enumeration type, a pointer, a pointer to member, or a const- + or volatile-qualified version of one of these types. + </listitem> + <listitem> + This quote is from Donald Knuth, ACM Computing Surveys, December 1974, pg + 268. + </listitem> + <listitem> + The test code is available as part of the boost utility library (see algo_opt_examples.cpp), + the code was compiled with gcc 2.95 with all optimisations turned on, tests + were conducted on a 400MHz Pentium II machine running Microsoft Windows 98. + </listitem> + <listitem> + John Maddock and Howard Hinnant have submitted a "compressed_pair" + library to Boost, which uses a technique similar to the one described here + to hold references. Their pair also uses type traits to determine if any + of the types are empty, and will derive instead of contain to conserve space + -- hence the name "compressed". + </listitem> + <listitem> + This is actually an issue with the C++ Core Language Working Group (issue + #106), submitted by Bjarne Stroustrup. The tentative resolution is to allow + a "reference to a reference to T" to mean the same thing as a "reference + to T", but only in template instantiation, in a method similar to multiple + cv-qualifiers. + </listitem> + <listitem> + For those of you who are wondering why this shouldn't be const-qualified, + remember that references are always implicitly constant (for example, you + can't re-assign a reference). Remember also that "const T &" + is something completely different. For this reason, cv-qualifiers on template + type arguments that are references are ignored. + </listitem> + </orderedlist> + </section> + <section id="boost_typetraits.category"> + <title><link linkend="boost_typetraits.category"> Type Traits by Category</link></title> + <section id="boost_typetraits.category.value_traits"> + <title><link linkend="boost_typetraits.category.value_traits"> Type Traits + that Describe the Properties of a Type</link></title> + <para> + <indexterm> + <primary>Foo2</primary> + <secondary>Bar2</secondary> + </indexterm> + These traits are all <emphasis>value traits</emphasis>, which is to say the + traits classes all inherit from <link linkend="boost_typetraits.reference.integral_constant">integral_constant</link>, + and are used to access some numerical property of a type. Often this is a + simple true or false Boolean value, but in a few cases may be some other + integer value (for example when dealing with type alignments, or array bounds: + see <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.alignment_of">alignment_of</link></computeroutput>, + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.rank">rank</link></computeroutput> + and <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.extent">extent</link></computeroutput>). + </para> + <section id="boost_typetraits.category.value_traits.primary"> + <title><link linkend="boost_typetraits.category.value_traits.primary"> Categorizing + a Type</link></title> + <para> + These traits identify what "kind" of type some type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> is. These are split into two groups: + primary traits which are all mutually exclusive, and composite traits that + are compositions of one or more primary traits. + </para> + <para> + For any given type, exactly one primary type trait will inherit from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + and all the others will inherit from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>, + in other words these traits are mutually exclusive. + </para> + <para> + This means that <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.is_integral">is_integral</link><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> + and <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.is_floating_point">is_floating_point</link><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> + will only ever be true for built-in types; if you want to check for a user-defined + class type that behaves "as if" it is an integral or floating + point type, then use the <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">numeric_limits</phrase> + <phrase role="keyword">template</phrase></computeroutput> instead. + </para> + <para> + <emphasis role="bold">Synopsis:</emphasis> + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_array">is_array</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_class">is_class</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_complex">is_complex</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_enum">is_enum</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_floating_point">is_floating_point</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_function">is_function</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_integral">is_integral</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_member_function_pointer">is_member_function_pointer</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_member_object_pointer">is_member_object_pointer</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_pointer">is_pointer</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_reference">is_reference</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_union">is_union</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_void">is_void</link><phrase role="special">;</phrase> +</programlisting> + <para> + The following traits are made up of the union of one or more type categorizations. + A type may belong to more than one of these categories, in addition to + one of the primary categories. + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_arithmetic">is_arithmetic</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_compound">is_compound</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_fundamental">is_fundamental</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_member_pointer">is_member_pointer</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_object">is_object</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_scalar">is_scalar</link><phrase role="special">;</phrase> +</programlisting> + </section> + <section id="boost_typetraits.category.value_traits.properties"> + <title><link linkend="boost_typetraits.category.value_traits.properties"> + General Type Properties</link></title> + <para> + The following templates describe the general properties of a type. + </para> + <para> + <emphasis role="bold">Synopsis:</emphasis> + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.alignment_of">alignment_of</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.has_nothrow_assign">has_nothrow_assign</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.has_nothrow_constructor">has_nothrow_constructor</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.has_nothrow_constructor">has_nothrow_default_constructor</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.has_nothrow_copy">has_nothrow_copy</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.has_nothrow_copy">has_nothrow_copy_constructor</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.has_trivial_assign">has_trivial_assign</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.has_trivial_constructor">has_trivial_constructor</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.has_trivial_constructor">has_trivial_default_constructor</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.has_trivial_copy">has_trivial_copy</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.has_trivial_copy">has_trivial_copy_constructor</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.has_trivial_destructor">has_trivial_destructor</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.has_virtual_destructor">has_virtual_destructor</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_abstract">is_abstract</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_const">is_const</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_empty">is_empty</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_stateless">is_stateless</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_pod">is_pod</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_polymorphic">is_polymorphic</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_signed">is_signed</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_unsigned">is_unsigned</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_volatile">is_volatile</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">,</phrase> <phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase> <phrase role="identifier">N</phrase> <phrase role="special">=</phrase> <phrase role="number">0</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.extent">extent</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.rank">rank</link><phrase role="special">;</phrase> +</programlisting> + </section> + <section id="boost_typetraits.category.value_traits.relate"> + <title><link linkend="boost_typetraits.category.value_traits.relate"> Relationships + Between Two Types</link></title> + <para> + These templates determine the whether there is a relationship between two + types: + </para> + <para> + <emphasis role="bold">Synopsis:</emphasis> + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">Base</phrase><phrase role="special">,</phrase> <phrase role="keyword">class</phrase> <phrase role="identifier">Derived</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_base_of">is_base_of</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">From</phrase><phrase role="special">,</phrase> <phrase role="keyword">class</phrase> <phrase role="identifier">To</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_convertible">is_convertible</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">,</phrase> <phrase role="keyword">class</phrase> <phrase role="identifier">U</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_same">is_same</link><phrase role="special">;</phrase> +</programlisting> + </section> + </section> + <section id="boost_typetraits.category.transform"><indexterm type="macro_name"><primary>BOOST_BROKEN_COMPILER_TYPE_TRAITS_SPECIALIZATION</primary><secondary>Type Traits that Transform One Type to Another</secondary></indexterm><indexterm><primary>Type Traits that Transform One Type to Another</primary><secondary>BOOST_BROKEN_COMPILER_TYPE_TRAITS_SPECIALIZATION</secondary></indexterm><indexterm type="macro_name"><primary>BOOST_BROKEN_COMPILER_TYPE_TRAITS_SPECIALIZATION</primary><secondary>Type Traits that Transform One Type to Another</secondary></indexterm><indexterm><primary>Type Traits that Transform One Type to Another</primary><secondary>BOOST_BROKEN_COMPILER_TYPE_TRAITS_SPECIALIZATION</secondary></indexterm> + <title><link linkend="boost_typetraits.category.transform"> Type Traits that + Transform One Type to Another</link></title> + <para> + The following templates transform one type to another, based upon some well-defined + rule. Each template has a single member called <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">type</phrase></computeroutput> + that is the result of applying the transformation to the template argument + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput>. + </para> + <para> + <emphasis role="bold">Synopsis:</emphasis> + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.add_const">add_const</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.add_cv">add_cv</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.add_pointer">add_pointer</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.add_reference">add_reference</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.add_volatile">add_volatile</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.decay">decay</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.floating_point_promotion">floating_point_promotion</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.integral_promotion">integral_promotion</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.make_signed">make_signed</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.make_unsigned">make_unsigned</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.promote">promote</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.remove_all_extents">remove_all_extents</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.remove_const">remove_const</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.remove_cv">remove_cv</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.remove_extent">remove_extent</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.remove_pointer">remove_pointer</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.remove_reference">remove_reference</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.remove_volatile">remove_volatile</link><phrase role="special">;</phrase> +</programlisting> + <anchor id="boost_typetraits.category.transform.broken_compiler_workarounds_"/> + <bridgehead renderas="sect4"> + <link linkend="boost_typetraits.category.transform.broken_compiler_workarounds_">Broken + Compiler Workarounds:</link> + </bridgehead> + <para> + For all of these templates support for partial specialization of class templates + is required to correctly implement the transformation. On the other hand, + practice shows that many of the templates from this category are very useful, + and often essential for implementing some generic libraries. Lack of these + templates is often one of the major limiting factors in porting those libraries + to compilers that do not yet support this language feature. As some of these + compilers are going to be around for a while, and at least one of them is + very wide-spread, it was decided that the library should provide workarounds + where possible. + </para> + <para> + The basic idea behind the workaround is to manually define full specializations + of all type transformation templates for all fundamental types, and all their + 1st and 2nd rank cv-[un]qualified derivative pointer types, and to provide + a user-level macro that will define all the explicit specializations needed + for any user-defined type T. + </para> + <para> + The first part guarantees the successful compilation of something like this: + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">BOOST_STATIC_ASSERT</phrase><phrase role="special">((</phrase><phrase role="identifier">is_same</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase><phrase role="special">,</phrase> <phrase role="identifier">remove_reference</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase><phrase role="special">&>::</phrase><phrase role="identifier">type</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase><phrase role="special">));</phrase> +<phrase role="identifier">BOOST_STATIC_ASSERT</phrase><phrase role="special">((</phrase><phrase role="identifier">is_same</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase> <phrase role="keyword">const</phrase><phrase role="special">,</phrase> <phrase role="identifier">remove_reference</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase> <phrase role="keyword">const</phrase><phrase role="special">&>::</phrase><phrase role="identifier">type</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase><phrase role="special">));</phrase> +<phrase role="identifier">BOOST_STATIC_ASSERT</phrase><phrase role="special">((</phrase><phrase role="identifier">is_same</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase> <phrase role="keyword">volatile</phrase><phrase role="special">,</phrase> <phrase role="identifier">remove_reference</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase> <phrase role="keyword">volatile</phrase><phrase role="special">&>::</phrase><phrase role="identifier">type</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase><phrase role="special">));</phrase> +<phrase role="identifier">BOOST_STATIC_ASSERT</phrase><phrase role="special">((</phrase><phrase role="identifier">is_same</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase> <phrase role="keyword">const</phrase> <phrase role="keyword">volatile</phrase><phrase role="special">,</phrase> <phrase role="identifier">remove_reference</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase> <phrase role="keyword">const</phrase> <phrase role="keyword">volatile</phrase><phrase role="special">&>::</phrase><phrase role="identifier">type</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase><phrase role="special">));</phrase> +<phrase role="identifier">BOOST_STATIC_ASSERT</phrase><phrase role="special">((</phrase><phrase role="identifier">is_same</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase><phrase role="special">*,</phrase> <phrase role="identifier">remove_reference</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase><phrase role="special">*&>::</phrase><phrase role="identifier">type</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase><phrase role="special">));</phrase> +<phrase role="identifier">BOOST_STATIC_ASSERT</phrase><phrase role="special">((</phrase><phrase role="identifier">is_same</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase> <phrase role="keyword">const</phrase><phrase role="special">*,</phrase> <phrase role="identifier">remove_reference</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase> <phrase role="keyword">const</phrase><phrase role="special">*&>::</phrase><phrase role="identifier">type</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase><phrase role="special">));</phrase> +<phrase role="special">...</phrase> +<phrase role="identifier">BOOST_STATIC_ASSERT</phrase><phrase role="special">((</phrase><phrase role="identifier">is_same</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase> <phrase role="keyword">const</phrase> <phrase role="keyword">volatile</phrase><phrase role="special">*</phrase> <phrase role="keyword">const</phrase> <phrase role="keyword">volatile</phrase><phrase role="special">*</phrase> <phrase role="keyword">const</phrase> <phrase role="keyword">volatile</phrase><phrase role="special">,</phrase> <phrase role="identifier">remove_reference</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase> <phrase role="keyword">const</phrase> <phrase role="keyword">volatile</phrase><phrase role="special">*</phrase> <phrase role="keyword">const</phrase> <phrase role="keyword">volatile</phrase><phrase role="special">*</phrase> <phrase role="keyword">const</phrase> <phrase role="keyword">volatile</phrase><phrase role="special">&>::</phrase><phrase role="identifier">type</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase><phrase role="special">));</phrase> +</programlisting> + <para> + and the second part provides the library's users with a mechanism to make + the above code work not only for <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">char</phrase></computeroutput>, + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase></computeroutput> or other built-in type, + but for their own types as well: + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">namespace</phrase> <phrase role="identifier">myspace</phrase><phrase role="special">{</phrase> + <phrase role="keyword">struct</phrase> <phrase role="identifier">MyClass</phrase> <phrase role="special">{};</phrase> +<phrase role="special">}</phrase> +<phrase role="comment">// declare this at global scope: +</phrase><phrase role="identifier">BOOST_BROKEN_COMPILER_TYPE_TRAITS_SPECIALIZATION</phrase><phrase role="special">(</phrase><phrase role="identifier">myspace</phrase><phrase role="special">::</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">)</phrase> +<phrase role="comment">// transformations on myspace::MyClass now work: +</phrase><phrase role="identifier">BOOST_STATIC_ASSERT</phrase><phrase role="special">((</phrase><phrase role="identifier">is_same</phrase><phrase role="special"><</phrase><phrase role="identifier">myspace</phrase><phrase role="special">::</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">,</phrase> <phrase role="identifier">remove_reference</phrase><phrase role="special"><</phrase><phrase role="identifier">myspace</phrase><phrase role="special">::</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">&>::</phrase><phrase role="identifier">type</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase><phrase role="special">));</phrase> +<phrase role="identifier">BOOST_STATIC_ASSERT</phrase><phrase role="special">((</phrase><phrase role="identifier">is_same</phrase><phrase role="special"><</phrase><phrase role="identifier">myspace</phrase><phrase role="special">::</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">,</phrase> <phrase role="identifier">remove_const</phrase><phrase role="special"><</phrase><phrase role="identifier">myspace</phrase><phrase role="special">::</phrase><phrase role="identifier">MyClass</phrase> <phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase><phrase role="special">));</phrase> +<phrase role="comment">// etc. +</phrase></programlisting> + <para> + Note that the macro BOOST_BROKEN_COMPILER_TYPE_TRAITS_SPECIALIZATION evaluates + to nothing on those compilers that <emphasis role="bold">do</emphasis> support + partial specialization. + </para> + </section> + <section id="boost_typetraits.category.alignment"> + <title><link linkend="boost_typetraits.category.alignment"> Synthesizing Types + with Specific Alignments</link></title> + <para> + Some low level memory management routines need to synthesize a POD type with + specific alignment properties. The template <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.type_with_alignment">type_with_alignment</link></computeroutput> + finds the smallest type with a specified alignment, while template <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.aligned_storage">aligned_storage</link></computeroutput> + creates a type with a specific size and alignment. + </para> + <para> + <emphasis role="bold">Synopsis</emphasis> + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase> <phrase role="identifier">Align</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.type_with_alignment">type_with_alignment</link><phrase role="special">;</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase> <phrase role="identifier">Size</phrase><phrase role="special">,</phrase> <phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase> <phrase role="identifier">Align</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.aligned_storage">aligned_storage</link><phrase role="special">;</phrase> +</programlisting> + </section> + <section id="boost_typetraits.category.function"> + <title><link linkend="boost_typetraits.category.function"> Decomposing Function + Types</link></title> + <para> + The class template <link linkend="boost_typetraits.reference.function_traits">function_traits</link> + extracts information from function types (see also <link linkend="boost_typetraits.reference.is_function">is_function</link>). + This traits class allows you to tell how many arguments a function takes, + what those argument types are, and what the return type is. + </para> + <para> + <emphasis role="bold">Synopsis</emphasis> + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase> <phrase role="identifier">Align</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.function_traits">function_traits</link><phrase role="special">;</phrase> +</programlisting> + </section> + </section> + <section id="boost_typetraits.user_defined"><indexterm type="class_name"><primary>is_union</primary><secondary>User Defined Specializations</secondary></indexterm><indexterm><primary>User Defined Specializations</primary><secondary>is_union</secondary></indexterm><indexterm type="class_name"><primary>is_class</primary><secondary>User Defined Specializations</secondary></indexterm><indexterm><primary>User Defined Specializations</primary><secondary>is_class</secondary></indexterm> + <title><link linkend="boost_typetraits.user_defined"> User Defined Specializations</link></title> + <para> + Occationally the end user may need to provide their own specialization for + one of the type traits - typically where intrinsic compiler support is required + to implement a specific trait fully. These specializations should derive from + boost::<link linkend="boost_typetraits.reference.integral_constant">true_type</link> + or boost::<link linkend="boost_typetraits.reference.integral_constant">false_type</link> + as appropriate: + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_pod</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase> +<phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_class</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase> +<phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_union</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase> + +<phrase role="keyword">struct</phrase> <phrase role="identifier">my_pod</phrase><phrase role="special">{};</phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">my_union</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">char</phrase> <phrase role="identifier">c</phrase><phrase role="special">;</phrase> + <phrase role="keyword">int</phrase> <phrase role="identifier">i</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> + +<phrase role="keyword">namespace</phrase> <phrase role="identifier">boost</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">template</phrase><phrase role="special"><></phrase> + <phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_pod">is_pod</link><phrase role="special"><</phrase><phrase role="identifier">my_pod</phrase><phrase role="special">></phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <link linkend="boost_typetraits.reference.integral_constant">true_type</link><phrase role="special">{};</phrase> + + <phrase role="keyword">template</phrase><phrase role="special"><></phrase> + <phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_pod">is_pod</link><phrase role="special"><</phrase><phrase role="identifier">my_union</phrase><phrase role="special">></phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <link linkend="boost_typetraits.reference.integral_constant">true_type</link><phrase role="special">{};</phrase> + + <phrase role="keyword">template</phrase><phrase role="special"><></phrase> + <phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_union">is_union</link><phrase role="special"><</phrase><phrase role="identifier">my_union</phrase><phrase role="special">></phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <link linkend="boost_typetraits.reference.integral_constant">true_type</link><phrase role="special">{};</phrase> + + <phrase role="keyword">template</phrase><phrase role="special"><></phrase> + <phrase role="keyword">struct</phrase> <link linkend="boost_typetraits.reference.is_class">is_class</link><phrase role="special"><</phrase><phrase role="identifier">my_union</phrase><phrase role="special">></phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <link linkend="boost_typetraits.reference.integral_constant">false_type</link><phrase role="special">{};</phrase> +<phrase role="special">}</phrase> +</programlisting> + </section> + <section id="boost_typetraits.intrinsics"><indexterm type="macro_name"><primary>BOOST_IS_UNION</primary><secondary>Support for Compiler Intrinsics</secondary></indexterm><indexterm><primary>Support for Compiler Intrinsics</primary><secondary>BOOST_IS_UNION</secondary></indexterm><indexterm type="macro_name"><primary>BOOST_IS_POLYMORPHIC</primary><secondary>Support for Compiler Intrinsics</secondary></indexterm><indexterm><primary>Support for Compiler Intrinsics</primary><secondary>BOOST_IS_POLYMORPHIC</secondary></indexterm><indexterm type="macro_name"><primary>BOOST_IS_POD</primary><secondary>Support for Compiler Intrinsics</secondary></indexterm><indexterm><primary>Support for Compiler Intrinsics</primary><secondary>BOOST_IS_POD</secondary></indexterm><indexterm type="macro_name"><primary>BOOST_IS_ENUM</primary><secondary>Support for Compiler Intrinsics</secondary></indexterm><indexterm><primary>Support for Compiler Intrinsics</primary><secondary>BOOST_IS_ENUM</secondary></indexterm><indexterm type="macro_name"><primary>BOOST_IS_EMPTY</primary><secondary>Support for Compiler Intrinsics</secondary></indexterm><indexterm><primary>Support for Compiler Intrinsics</primary><secondary>BOOST_IS_EMPTY</secondary></indexterm><indexterm type="macro_name"><primary>BOOST_IS_CONVERTIBLE</primary><secondary>Support for Compiler Intrinsics</secondary></indexterm><indexterm><primary>Support for Compiler Intrinsics</primary><secondary>BOOST_IS_CONVERTIBLE</secondary></indexterm><indexterm type="macro_name"><primary>BOOST_IS_CLASS</primary><secondary>Support for Compiler Intrinsics</secondary></indexterm><indexterm><primary>Support for Compiler Intrinsics</primary><secondary>BOOST_IS_CLASS</secondary></indexterm><indexterm type="macro_name"><primary>BOOST_IS_BASE_OF</primary><secondary>Support for Compiler Intrinsics</secondary></indexterm><indexterm><primary>Support for Compiler Intrinsics</primary><secondary>BOOST_IS_BASE_OF</secondary></indexterm><indexterm type="macro_name"><primary>BOOST_IS_ABSTRACT</primary><secondary>Support for Compiler Intrinsics</secondary></indexterm><indexterm><primary>Support for Compiler Intrinsics</primary><secondary>BOOST_IS_ABSTRACT</secondary></indexterm><indexterm type="macro_name"><primary>BOOST_HAS_VIRTUAL_DESTRUCTOR</primary><secondary>Support for Compiler Intrinsics</secondary></indexterm><indexterm><primary>Support for Compiler Intrinsics</primary><secondary>BOOST_HAS_VIRTUAL_DESTRUCTOR</secondary></indexterm><indexterm type="macro_name"><primary>BOOST_HAS_TRIVIAL_DESTRUCTOR</primary><secondary>Support for Compiler Intrinsics</secondary></indexterm><indexterm><primary>Support for Compiler Intrinsics</primary><secondary>BOOST_HAS_TRIVIAL_DESTRUCTOR</secondary></indexterm><indexterm type="macro_name"><primary>BOOST_HAS_TRIVIAL_COPY</primary><secondary>Support for Compiler Intrinsics</secondary></indexterm><indexterm><primary>Support for Compiler Intrinsics</primary><secondary>BOOST_HAS_TRIVIAL_COPY</secondary></indexterm><indexterm type="macro_name"><primary>BOOST_HAS_TRIVIAL_CONSTRUCTOR</primary><secondary>Support for Compiler Intrinsics</secondary></indexterm><indexterm><primary>Support for Compiler Intrinsics</primary><secondary>BOOST_HAS_TRIVIAL_CONSTRUCTOR</secondary></indexterm><indexterm type="macro_name"><primary>BOOST_HAS_TRIVIAL_ASSIGN</primary><secondary>Support for Compiler Intrinsics</secondary></indexterm><indexterm><primary>Support for Compiler Intrinsics</primary><secondary>BOOST_HAS_TRIVIAL_ASSIGN</secondary></indexterm><indexterm type="macro_name"><primary>BOOST_HAS_NOTHROW_COPY</primary><secondary>Support for Compiler Intrinsics</secondary></indexterm><indexterm><primary>Support for Compiler Intrinsics</primary><secondary>BOOST_HAS_NOTHROW_COPY</secondary></indexterm><indexterm type="macro_name"><primary>BOOST_HAS_NOTHROW_CONSTRUCTOR</primary><secondary>Support for Compiler Intrinsics</secondary></indexterm><indexterm><primary>Support for Compiler Intrinsics</primary><secondary>BOOST_HAS_NOTHROW_CONSTRUCTOR</secondary></indexterm><indexterm type="macro_name"><primary>BOOST_HAS_NOTHROW_ASSIGN</primary><secondary>Support for Compiler Intrinsics</secondary></indexterm><indexterm><primary>Support for Compiler Intrinsics</primary><secondary>BOOST_HAS_NOTHROW_ASSIGN</secondary></indexterm><indexterm type="macro_name"><primary>BOOST_ALIGNMENT_OF</primary><secondary>Support for Compiler Intrinsics</secondary></indexterm><indexterm><primary>Support for Compiler Intrinsics</primary><secondary>BOOST_ALIGNMENT_OF</secondary></indexterm> + <title><link linkend="boost_typetraits.intrinsics"> Support for Compiler Intrinsics</link></title> + <para> + There are some traits that can not be implemented within the current C++ language: + to make these traits "just work" with user defined types, some kind + of additional help from the compiler is required. Currently (April 2008) Visual + C++ 8 and 9, GNU GCC 4.3 and MWCW 9 provide the necessary intrinsics, and other + compilers will no doubt follow in due course. + </para> + <para> + The Following traits classes always need compiler support to do the right thing + for all types (but all have safe fallback positions if this support is unavailable): + </para> + <itemizedlist> + <listitem> + <link linkend="boost_typetraits.reference.is_union">is_union</link> + </listitem> + <listitem> + <link linkend="boost_typetraits.reference.is_pod">is_pod</link> + </listitem> + <listitem> + <link linkend="boost_typetraits.reference.has_trivial_constructor">has_trivial_constructor</link> + </listitem> + <listitem> + <link linkend="boost_typetraits.reference.has_trivial_copy">has_trivial_copy</link> + </listitem> + <listitem> + <link linkend="boost_typetraits.reference.has_trivial_assign">has_trivial_assign</link> + </listitem> + <listitem> + <link linkend="boost_typetraits.reference.has_trivial_destructor">has_trivial_destructor</link> + </listitem> + <listitem> + <link linkend="boost_typetraits.reference.has_nothrow_constructor">has_nothrow_constructor</link> + </listitem> + <listitem> + <link linkend="boost_typetraits.reference.has_nothrow_copy">has_nothrow_copy</link> + </listitem> + <listitem> + <link linkend="boost_typetraits.reference.has_nothrow_assign">has_nothrow_assign</link> + </listitem> + <listitem> + <link linkend="boost_typetraits.reference.has_virtual_destructor">has_virtual_destructor</link> + </listitem> + </itemizedlist> + <para> + The following traits classes can't be portably implemented in the C++ language, + although in practice, the implementations do in fact do the right thing on + all the compilers we know about: + </para> + <itemizedlist> + <listitem> + <link linkend="boost_typetraits.reference.is_empty">is_empty</link> + </listitem> + <listitem> + <link linkend="boost_typetraits.reference.is_polymorphic">is_polymorphic</link> + </listitem> + </itemizedlist> + <para> + The following traits classes are dependent on one or more of the above: + </para> + <itemizedlist> + <listitem> + <link linkend="boost_typetraits.reference.is_class">is_class</link> + </listitem> + <listitem> + <link linkend="boost_typetraits.reference.is_stateless">is_stateless</link> + </listitem> + </itemizedlist> + <para> + The hooks for compiler-intrinsic support are defined in <ulink url="../../../../boost/type_traits/intrinsics.hpp">boost/type_traits/intrinsics.hpp</ulink>, + adding support for new compilers is simply a matter of defining one of more + of the following macros: + </para> + <table frame="all"> <title>Macros for Compiler Intrinsics</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + BOOST_IS_UNION(T) + </para> + </entry><entry> + <para> + Should evaluate to true if T is a union type + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + BOOST_IS_POD(T) + </para> + </entry><entry> + <para> + Should evaluate to true if T is a POD type + </para> + </entry> + </row> + <row> + <entry> + <para> + BOOST_IS_EMPTY(T) + </para> + </entry><entry> + <para> + Should evaluate to true if T is an empty struct or union + </para> + </entry> + </row> + <row> + <entry> + <para> + BOOST_HAS_TRIVIAL_CONSTRUCTOR(T) + </para> + </entry><entry> + <para> + Should evaluate to true if the default constructor for T is trivial (i.e. + has no effect) + </para> + </entry> + </row> + <row> + <entry> + <para> + BOOST_HAS_TRIVIAL_COPY(T) + </para> + </entry><entry> + <para> + Should evaluate to true if T has a trivial copy constructor (and can + therefore be replaced by a call to memcpy) + </para> + </entry> + </row> + <row> + <entry> + <para> + BOOST_HAS_TRIVIAL_ASSIGN(T) + </para> + </entry><entry> + <para> + Should evaluate to true if T has a trivial assignment operator (and can + therefore be replaced by a call to memcpy) + </para> + </entry> + </row> + <row> + <entry> + <para> + BOOST_HAS_TRIVIAL_DESTRUCTOR(T) + </para> + </entry><entry> + <para> + Should evaluate to true if T has a trivial destructor (i.e. ~T() has + no effect) + </para> + </entry> + </row> + <row> + <entry> + <para> + BOOST_HAS_NOTHROW_CONSTRUCTOR(T) + </para> + </entry><entry> + <para> + Should evaluate to true if <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase> + <phrase role="identifier">x</phrase><phrase role="special">;</phrase></computeroutput> + can not throw + </para> + </entry> + </row> + <row> + <entry> + <para> + BOOST_HAS_NOTHROW_COPY(T) + </para> + </entry><entry> + <para> + Should evaluate to true if <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase><phrase role="special">(</phrase><phrase role="identifier">t</phrase><phrase role="special">)</phrase></computeroutput> can not throw + </para> + </entry> + </row> + <row> + <entry> + <para> + BOOST_HAS_NOTHROW_ASSIGN(T) + </para> + </entry><entry> + <para> + Should evaluate to true if <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase> + <phrase role="identifier">t</phrase><phrase role="special">,</phrase> + <phrase role="identifier">u</phrase><phrase role="special">;</phrase> + <phrase role="identifier">t</phrase> <phrase role="special">=</phrase> + <phrase role="identifier">u</phrase></computeroutput> can not throw + </para> + </entry> + </row> + <row> + <entry> + <para> + BOOST_HAS_VIRTUAL_DESTRUCTOR(T) + </para> + </entry><entry> + <para> + Should evaluate to true T has a virtual destructor + </para> + </entry> + </row> + <row> + <entry> + <para> + BOOST_IS_ABSTRACT(T) + </para> + </entry><entry> + <para> + Should evaluate to true if T is an abstract type + </para> + </entry> + </row> + <row> + <entry> + <para> + BOOST_IS_BASE_OF(T,U) + </para> + </entry><entry> + <para> + Should evaluate to true if T is a base class of U + </para> + </entry> + </row> + <row> + <entry> + <para> + BOOST_IS_CLASS(T) + </para> + </entry><entry> + <para> + Should evaluate to true if T is a class type + </para> + </entry> + </row> + <row> + <entry> + <para> + BOOST_IS_CONVERTIBLE(T,U) + </para> + </entry><entry> + <para> + Should evaluate to true if T is convertible to U + </para> + </entry> + </row> + <row> + <entry> + <para> + BOOST_IS_ENUM(T) + </para> + </entry><entry> + <para> + Should evaluate to true is T is an enum + </para> + </entry> + </row> + <row> + <entry> + <para> + BOOST_IS_POLYMORPHIC(T) + </para> + </entry><entry> + <para> + Should evaluate to true if T is a polymorphic type + </para> + </entry> + </row> + <row> + <entry> + <para> + BOOST_ALIGNMENT_OF(T) + </para> + </entry><entry> + <para> + Should evaluate to the alignment requirements of type T. + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section id="boost_typetraits.mpl"> + <title><link linkend="boost_typetraits.mpl"> MPL Interoperability</link></title> + <para> + All the value based traits in this library conform to MPL's requirements for + an <ulink url="../../../../libs/mpl/doc/refmanual/integral-constant.html">Integral + Constant type</ulink>: that includes a number of rather intrusive workarounds + for broken compilers. + </para> + <para> + Purely as an implementation detail, this means that <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput> + inherits from <ulink url="../../../../libs/mpl/doc/refmanual/bool.html"><computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">boost</phrase><phrase role="special">::</phrase><phrase role="identifier">mpl</phrase><phrase role="special">::</phrase><phrase role="identifier">true_</phrase></computeroutput></ulink>, + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">false_type</link></computeroutput> + inherits from <ulink url="../../../../libs/mpl/doc/refmanual/bool.html"><computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">boost</phrase><phrase role="special">::</phrase><phrase role="identifier">mpl</phrase><phrase role="special">::</phrase><phrase role="identifier">false_</phrase></computeroutput></ulink>, + and <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">integral_constant</link><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">,</phrase> + <phrase role="identifier">v</phrase><phrase role="special">></phrase></computeroutput> + inherits from <ulink url="../../../../libs/mpl/doc/refmanual/integral-c.html"><computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">boost</phrase><phrase role="special">::</phrase><phrase role="identifier">mpl</phrase><phrase role="special">::</phrase><phrase role="identifier">integral_c</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">,</phrase><phrase role="identifier">v</phrase><phrase role="special">></phrase></computeroutput></ulink> + (provided <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> is not <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>) + </para> + </section> + <section id="boost_typetraits.examples"> + <title><link linkend="boost_typetraits.examples"> Examples</link></title> + <section id="boost_typetraits.examples.copy"><indexterm type="typedef_name"><primary>value_type</primary><secondary>An Optimized Version of std::copy</secondary></indexterm><indexterm><primary>Optimized Version of std::copy</primary><secondary>value_type</secondary></indexterm> + <title><link linkend="boost_typetraits.examples.copy"> An Optimized Version + of std::copy</link></title> + <para> + Demonstrates a version of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">copy</phrase></computeroutput> + that uses <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.has_trivial_assign">has_trivial_assign</link></computeroutput> + to determine whether to use <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">memcpy</phrase></computeroutput> + to optimise the copy operation (see <ulink url="../../examples/copy_example.cpp">copy_example.cpp</ulink>): + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="comment">// +</phrase><phrase role="comment">// opt::copy +</phrase><phrase role="comment">// same semantics as std::copy +</phrase><phrase role="comment">// calls memcpy where appropriate. +</phrase><phrase role="comment">// +</phrase> +<phrase role="keyword">namespace</phrase> <phrase role="identifier">detail</phrase><phrase role="special">{</phrase> + +<phrase role="keyword">template</phrase><phrase role="special"><</phrase><phrase role="keyword">typename</phrase> <phrase role="identifier">I1</phrase><phrase role="special">,</phrase> <phrase role="keyword">typename</phrase> <phrase role="identifier">I2</phrase><phrase role="special">,</phrase> <phrase role="keyword">bool</phrase> <phrase role="identifier">b</phrase><phrase role="special">></phrase> +<phrase role="identifier">I2</phrase> <phrase role="identifier">copy_imp</phrase><phrase role="special">(</phrase><phrase role="identifier">I1</phrase> <phrase role="identifier">first</phrase><phrase role="special">,</phrase> <phrase role="identifier">I1</phrase> <phrase role="identifier">last</phrase><phrase role="special">,</phrase> <phrase role="identifier">I2</phrase> <phrase role="identifier">out</phrase><phrase role="special">,</phrase> <phrase role="keyword">const</phrase> <phrase role="identifier">boost</phrase><phrase role="special">::</phrase><link linkend="boost_typetraits.reference.integral_constant">integral_constant</link><phrase role="special"><</phrase><phrase role="keyword">bool</phrase><phrase role="special">,</phrase> <phrase role="identifier">b</phrase><phrase role="special">>&)</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">while</phrase><phrase role="special">(</phrase><phrase role="identifier">first</phrase> <phrase role="special">!=</phrase> <phrase role="identifier">last</phrase><phrase role="special">)</phrase> + <phrase role="special">{</phrase> + <phrase role="special">*</phrase><phrase role="identifier">out</phrase> <phrase role="special">=</phrase> <phrase role="special">*</phrase><phrase role="identifier">first</phrase><phrase role="special">;</phrase> + <phrase role="special">++</phrase><phrase role="identifier">out</phrase><phrase role="special">;</phrase> + <phrase role="special">++</phrase><phrase role="identifier">first</phrase><phrase role="special">;</phrase> + <phrase role="special">}</phrase> + <phrase role="keyword">return</phrase> <phrase role="identifier">out</phrase><phrase role="special">;</phrase> +<phrase role="special">}</phrase> + +<phrase role="keyword">template</phrase><phrase role="special"><</phrase><phrase role="keyword">typename</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="identifier">T</phrase><phrase role="special">*</phrase> <phrase role="identifier">copy_imp</phrase><phrase role="special">(</phrase><phrase role="keyword">const</phrase> <phrase role="identifier">T</phrase><phrase role="special">*</phrase> <phrase role="identifier">first</phrase><phrase role="special">,</phrase> <phrase role="keyword">const</phrase> <phrase role="identifier">T</phrase><phrase role="special">*</phrase> <phrase role="identifier">last</phrase><phrase role="special">,</phrase> <phrase role="identifier">T</phrase><phrase role="special">*</phrase> <phrase role="identifier">out</phrase><phrase role="special">,</phrase> <phrase role="keyword">const</phrase> <phrase role="identifier">boost</phrase><phrase role="special">::</phrase><link linkend="boost_typetraits.reference.integral_constant">true_type</link><phrase role="special">&)</phrase> +<phrase role="special">{</phrase> + <phrase role="identifier">memcpy</phrase><phrase role="special">(</phrase><phrase role="identifier">out</phrase><phrase role="special">,</phrase> <phrase role="identifier">first</phrase><phrase role="special">,</phrase> <phrase role="special">(</phrase><phrase role="identifier">last</phrase><phrase role="special">-</phrase><phrase role="identifier">first</phrase><phrase role="special">)*</phrase><phrase role="keyword">sizeof</phrase><phrase role="special">(</phrase><phrase role="identifier">T</phrase><phrase role="special">));</phrase> + <phrase role="keyword">return</phrase> <phrase role="identifier">out</phrase><phrase role="special">+(</phrase><phrase role="identifier">last</phrase><phrase role="special">-</phrase><phrase role="identifier">first</phrase><phrase role="special">);</phrase> +<phrase role="special">}</phrase> + + +<phrase role="special">}</phrase> + +<phrase role="keyword">template</phrase><phrase role="special"><</phrase><phrase role="keyword">typename</phrase> <phrase role="identifier">I1</phrase><phrase role="special">,</phrase> <phrase role="keyword">typename</phrase> <phrase role="identifier">I2</phrase><phrase role="special">></phrase> +<phrase role="keyword">inline</phrase> <phrase role="identifier">I2</phrase> <phrase role="identifier">copy</phrase><phrase role="special">(</phrase><phrase role="identifier">I1</phrase> <phrase role="identifier">first</phrase><phrase role="special">,</phrase> <phrase role="identifier">I1</phrase> <phrase role="identifier">last</phrase><phrase role="special">,</phrase> <phrase role="identifier">I2</phrase> <phrase role="identifier">out</phrase><phrase role="special">)</phrase> +<phrase role="special">{</phrase> + <phrase role="comment">// +</phrase> <phrase role="comment">// We can copy with memcpy if T has a trivial assignment operator, +</phrase> <phrase role="comment">// and if the iterator arguments are actually pointers (this last +</phrase> <phrase role="comment">// requirement we detect with overload resolution): +</phrase> <phrase role="comment">// +</phrase> <phrase role="keyword">typedef</phrase> <phrase role="keyword">typename</phrase> <phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">iterator_traits</phrase><phrase role="special"><</phrase><phrase role="identifier">I1</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase> <phrase role="identifier">value_type</phrase><phrase role="special">;</phrase> + <phrase role="keyword">return</phrase> <phrase role="identifier">detail</phrase><phrase role="special">::</phrase><phrase role="identifier">copy_imp</phrase><phrase role="special">(</phrase><phrase role="identifier">first</phrase><phrase role="special">,</phrase> <phrase role="identifier">last</phrase><phrase role="special">,</phrase> <phrase role="identifier">out</phrase><phrase role="special">,</phrase> <phrase role="identifier">boost</phrase><phrase role="special">::</phrase><link linkend="boost_typetraits.reference.has_trivial_assign">has_trivial_assign</link><phrase role="special"><</phrase><phrase role="identifier">value_type</phrase><phrase role="special">>());</phrase> +<phrase role="special">}</phrase> +</programlisting> + </section> + <section id="boost_typetraits.examples.fill"> + <title><link linkend="boost_typetraits.examples.fill"> An Optimised Version + of std::fill</link></title> + <para> + Demonstrates a version of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">fill</phrase></computeroutput> + that uses <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.has_trivial_assign">has_trivial_assign</link></computeroutput> + to determine whether to use <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">memset</phrase></computeroutput> + to optimise the fill operation (see <ulink url="../../examples/fill_example.cpp">fill_example.cpp</ulink>): + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="comment">// +</phrase><phrase role="comment">// fill +</phrase><phrase role="comment">// same as std::fill, but uses memset where appropriate +</phrase><phrase role="comment">// +</phrase><phrase role="keyword">namespace</phrase> <phrase role="identifier">detail</phrase><phrase role="special">{</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">typename</phrase> <phrase role="identifier">I</phrase><phrase role="special">,</phrase> <phrase role="keyword">typename</phrase> <phrase role="identifier">T</phrase><phrase role="special">,</phrase> <phrase role="keyword">bool</phrase> <phrase role="identifier">b</phrase><phrase role="special">></phrase> +<phrase role="keyword">void</phrase> <phrase role="identifier">do_fill</phrase><phrase role="special">(</phrase><phrase role="identifier">I</phrase> <phrase role="identifier">first</phrase><phrase role="special">,</phrase> <phrase role="identifier">I</phrase> <phrase role="identifier">last</phrase><phrase role="special">,</phrase> <phrase role="keyword">const</phrase> <phrase role="identifier">T</phrase><phrase role="special">&</phrase> <phrase role="identifier">val</phrase><phrase role="special">,</phrase> <phrase role="keyword">const</phrase> <phrase role="identifier">boost</phrase><phrase role="special">::</phrase><link linkend="boost_typetraits.reference.integral_constant">integral_constant</link><phrase role="special"><</phrase><phrase role="keyword">bool</phrase><phrase role="special">,</phrase> <phrase role="identifier">b</phrase><phrase role="special">>&)</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">while</phrase><phrase role="special">(</phrase><phrase role="identifier">first</phrase> <phrase role="special">!=</phrase> <phrase role="identifier">last</phrase><phrase role="special">)</phrase> + <phrase role="special">{</phrase> + <phrase role="special">*</phrase><phrase role="identifier">first</phrase> <phrase role="special">=</phrase> <phrase role="identifier">val</phrase><phrase role="special">;</phrase> + <phrase role="special">++</phrase><phrase role="identifier">first</phrase><phrase role="special">;</phrase> + <phrase role="special">}</phrase> +<phrase role="special">}</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">typename</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">void</phrase> <phrase role="identifier">do_fill</phrase><phrase role="special">(</phrase><phrase role="identifier">T</phrase><phrase role="special">*</phrase> <phrase role="identifier">first</phrase><phrase role="special">,</phrase> <phrase role="identifier">T</phrase><phrase role="special">*</phrase> <phrase role="identifier">last</phrase><phrase role="special">,</phrase> <phrase role="keyword">const</phrase> <phrase role="identifier">T</phrase><phrase role="special">&</phrase> <phrase role="identifier">val</phrase><phrase role="special">,</phrase> <phrase role="keyword">const</phrase> <phrase role="identifier">boost</phrase><phrase role="special">::</phrase><link linkend="boost_typetraits.reference.integral_constant">true_type</link><phrase role="special">&)</phrase> +<phrase role="special">{</phrase> + <phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">memset</phrase><phrase role="special">(</phrase><phrase role="identifier">first</phrase><phrase role="special">,</phrase> <phrase role="identifier">val</phrase><phrase role="special">,</phrase> <phrase role="identifier">last</phrase><phrase role="special">-</phrase><phrase role="identifier">first</phrase><phrase role="special">);</phrase> +<phrase role="special">}</phrase> + +<phrase role="special">}</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">I</phrase><phrase role="special">,</phrase> <phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">inline</phrase> <phrase role="keyword">void</phrase> <phrase role="identifier">fill</phrase><phrase role="special">(</phrase><phrase role="identifier">I</phrase> <phrase role="identifier">first</phrase><phrase role="special">,</phrase> <phrase role="identifier">I</phrase> <phrase role="identifier">last</phrase><phrase role="special">,</phrase> <phrase role="keyword">const</phrase> <phrase role="identifier">T</phrase><phrase role="special">&</phrase> <phrase role="identifier">val</phrase><phrase role="special">)</phrase> +<phrase role="special">{</phrase> + <phrase role="comment">// +</phrase> <phrase role="comment">// We can do an optimised fill if T has a trivial assignment +</phrase> <phrase role="comment">// operator and if it's size is one: +</phrase> <phrase role="comment">// +</phrase> <phrase role="keyword">typedef</phrase> <phrase role="identifier">boost</phrase><phrase role="special">::</phrase><link linkend="boost_typetraits.reference.integral_constant">integral_constant</link><phrase role="special"><</phrase><phrase role="keyword">bool</phrase><phrase role="special">,</phrase> + <phrase role="special">::</phrase><phrase role="identifier">boost</phrase><phrase role="special">::</phrase><link linkend="boost_typetraits.reference.has_trivial_assign">has_trivial_assign</link><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase> <phrase role="special">&&</phrase> <phrase role="special">(</phrase><phrase role="keyword">sizeof</phrase><phrase role="special">(</phrase><phrase role="identifier">T</phrase><phrase role="special">)</phrase> <phrase role="special">==</phrase> <phrase role="number">1</phrase><phrase role="special">)></phrase> <phrase role="identifier">truth_type</phrase><phrase role="special">;</phrase> + <phrase role="identifier">detail</phrase><phrase role="special">::</phrase><phrase role="identifier">do_fill</phrase><phrase role="special">(</phrase><phrase role="identifier">first</phrase><phrase role="special">,</phrase> <phrase role="identifier">last</phrase><phrase role="special">,</phrase> <phrase role="identifier">val</phrase><phrase role="special">,</phrase> <phrase role="identifier">truth_type</phrase><phrase role="special">());</phrase> +<phrase role="special">}</phrase> +</programlisting> + </section> + <section id="boost_typetraits.examples.destruct"> + <title><link linkend="boost_typetraits.examples.destruct"> An Example that + Omits Destructor Calls For Types with Trivial Destructors</link></title> + <para> + Demonstrates a simple algorithm that uses <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">__has_trivial_destruct</phrase></computeroutput> + to determine whether to destructors need to be called (see <ulink url="../../examples/trivial_destructor_example.cpp">trivial_destructor_example.cpp</ulink>): + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="comment">// +</phrase><phrase role="comment">// algorithm destroy_array: +</phrase><phrase role="comment">// The reverse of std::unitialized_copy, takes a block of +</phrase><phrase role="comment">// initialized memory and calls destructors on all objects therein. +</phrase><phrase role="comment">// +</phrase> +<phrase role="keyword">namespace</phrase> <phrase role="identifier">detail</phrase><phrase role="special">{</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">void</phrase> <phrase role="identifier">do_destroy_array</phrase><phrase role="special">(</phrase><phrase role="identifier">T</phrase><phrase role="special">*</phrase> <phrase role="identifier">first</phrase><phrase role="special">,</phrase> <phrase role="identifier">T</phrase><phrase role="special">*</phrase> <phrase role="identifier">last</phrase><phrase role="special">,</phrase> <phrase role="keyword">const</phrase> <phrase role="identifier">boost</phrase><phrase role="special">::</phrase><link linkend="boost_typetraits.reference.integral_constant">false_type</link><phrase role="special">&)</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">while</phrase><phrase role="special">(</phrase><phrase role="identifier">first</phrase> <phrase role="special">!=</phrase> <phrase role="identifier">last</phrase><phrase role="special">)</phrase> + <phrase role="special">{</phrase> + <phrase role="identifier">first</phrase><phrase role="special">->~</phrase><phrase role="identifier">T</phrase><phrase role="special">();</phrase> + <phrase role="special">++</phrase><phrase role="identifier">first</phrase><phrase role="special">;</phrase> + <phrase role="special">}</phrase> +<phrase role="special">}</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">inline</phrase> <phrase role="keyword">void</phrase> <phrase role="identifier">do_destroy_array</phrase><phrase role="special">(</phrase><phrase role="identifier">T</phrase><phrase role="special">*</phrase> <phrase role="identifier">first</phrase><phrase role="special">,</phrase> <phrase role="identifier">T</phrase><phrase role="special">*</phrase> <phrase role="identifier">last</phrase><phrase role="special">,</phrase> <phrase role="keyword">const</phrase> <phrase role="identifier">boost</phrase><phrase role="special">::</phrase><link linkend="boost_typetraits.reference.integral_constant">true_type</link><phrase role="special">&)</phrase> +<phrase role="special">{</phrase> +<phrase role="special">}</phrase> + +<phrase role="special">}</phrase> <phrase role="comment">// namespace detail +</phrase> +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">inline</phrase> <phrase role="keyword">void</phrase> <phrase role="identifier">destroy_array</phrase><phrase role="special">(</phrase><phrase role="identifier">T</phrase><phrase role="special">*</phrase> <phrase role="identifier">p1</phrase><phrase role="special">,</phrase> <phrase role="identifier">T</phrase><phrase role="special">*</phrase> <phrase role="identifier">p2</phrase><phrase role="special">)</phrase> +<phrase role="special">{</phrase> + <phrase role="identifier">detail</phrase><phrase role="special">::</phrase><phrase role="identifier">do_destroy_array</phrase><phrase role="special">(</phrase><phrase role="identifier">p1</phrase><phrase role="special">,</phrase> <phrase role="identifier">p2</phrase><phrase role="special">,</phrase> <phrase role="special">::</phrase><phrase role="identifier">boost</phrase><phrase role="special">::</phrase><link linkend="boost_typetraits.reference.has_trivial_destructor">has_trivial_destructor</link><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>());</phrase> +<phrase role="special">}</phrase> +</programlisting> + </section> + <section id="boost_typetraits.examples.iter"> + <title><link linkend="boost_typetraits.examples.iter"> An improved Version + of std::iter_swap</link></title> + <para> + Demonstrates a version of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">iter_swap</phrase></computeroutput> + that use type traits to determine whether an it's arguments are proxying + iterators or not, if they're not then it just does a <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">swap</phrase></computeroutput> + of it's dereferenced arguments (the same as <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">iter_swap</phrase></computeroutput> + does), however if they are proxying iterators then takes special care over + the swap to ensure that the algorithm works correctly for both proxying iterators, + and even iterators of different types (see <ulink url="../../examples/iter_swap_example.cpp">iter_swap_example.cpp</ulink>): + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="comment">// +</phrase><phrase role="comment">// iter_swap: +</phrase><phrase role="comment">// tests whether iterator is a proxying iterator or not, and +</phrase><phrase role="comment">// uses optimal form accordingly: +</phrase><phrase role="comment">// +</phrase><phrase role="keyword">namespace</phrase> <phrase role="identifier">detail</phrase><phrase role="special">{</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">typename</phrase> <phrase role="identifier">I</phrase><phrase role="special">></phrase> +<phrase role="keyword">static</phrase> <phrase role="keyword">void</phrase> <phrase role="identifier">do_swap</phrase><phrase role="special">(</phrase><phrase role="identifier">I</phrase> <phrase role="identifier">one</phrase><phrase role="special">,</phrase> <phrase role="identifier">I</phrase> <phrase role="identifier">two</phrase><phrase role="special">,</phrase> <phrase role="keyword">const</phrase> <phrase role="identifier">boost</phrase><phrase role="special">::</phrase><link linkend="boost_typetraits.reference.integral_constant">false_type</link><phrase role="special">&)</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <phrase role="keyword">typename</phrase> <phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">iterator_traits</phrase><phrase role="special"><</phrase><phrase role="identifier">I</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase> <phrase role="identifier">v_t</phrase><phrase role="special">;</phrase> + <phrase role="identifier">v_t</phrase> <phrase role="identifier">v</phrase> <phrase role="special">=</phrase> <phrase role="special">*</phrase><phrase role="identifier">one</phrase><phrase role="special">;</phrase> + <phrase role="special">*</phrase><phrase role="identifier">one</phrase> <phrase role="special">=</phrase> <phrase role="special">*</phrase><phrase role="identifier">two</phrase><phrase role="special">;</phrase> + <phrase role="special">*</phrase><phrase role="identifier">two</phrase> <phrase role="special">=</phrase> <phrase role="identifier">v</phrase><phrase role="special">;</phrase> +<phrase role="special">}</phrase> +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">typename</phrase> <phrase role="identifier">I</phrase><phrase role="special">></phrase> +<phrase role="keyword">static</phrase> <phrase role="keyword">void</phrase> <phrase role="identifier">do_swap</phrase><phrase role="special">(</phrase><phrase role="identifier">I</phrase> <phrase role="identifier">one</phrase><phrase role="special">,</phrase> <phrase role="identifier">I</phrase> <phrase role="identifier">two</phrase><phrase role="special">,</phrase> <phrase role="keyword">const</phrase> <phrase role="identifier">boost</phrase><phrase role="special">::</phrase><link linkend="boost_typetraits.reference.integral_constant">true_type</link><phrase role="special">&)</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">using</phrase> <phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">swap</phrase><phrase role="special">;</phrase> + <phrase role="identifier">swap</phrase><phrase role="special">(*</phrase><phrase role="identifier">one</phrase><phrase role="special">,</phrase> <phrase role="special">*</phrase><phrase role="identifier">two</phrase><phrase role="special">);</phrase> +<phrase role="special">}</phrase> + +<phrase role="special">}</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">typename</phrase> <phrase role="identifier">I1</phrase><phrase role="special">,</phrase> <phrase role="keyword">typename</phrase> <phrase role="identifier">I2</phrase><phrase role="special">></phrase> +<phrase role="keyword">inline</phrase> <phrase role="keyword">void</phrase> <phrase role="identifier">iter_swap</phrase><phrase role="special">(</phrase><phrase role="identifier">I1</phrase> <phrase role="identifier">one</phrase><phrase role="special">,</phrase> <phrase role="identifier">I2</phrase> <phrase role="identifier">two</phrase><phrase role="special">)</phrase> +<phrase role="special">{</phrase> + <phrase role="comment">// +</phrase> <phrase role="comment">// See is both arguments are non-proxying iterators, +</phrase> <phrase role="comment">// and if both iterator the same type: +</phrase> <phrase role="comment">// +</phrase> <phrase role="keyword">typedef</phrase> <phrase role="keyword">typename</phrase> <phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">iterator_traits</phrase><phrase role="special"><</phrase><phrase role="identifier">I1</phrase><phrase role="special">>::</phrase><phrase role="identifier">reference</phrase> <phrase role="identifier">r1_t</phrase><phrase role="special">;</phrase> + <phrase role="keyword">typedef</phrase> <phrase role="keyword">typename</phrase> <phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">iterator_traits</phrase><phrase role="special"><</phrase><phrase role="identifier">I2</phrase><phrase role="special">>::</phrase><phrase role="identifier">reference</phrase> <phrase role="identifier">r2_t</phrase><phrase role="special">;</phrase> + + <phrase role="keyword">typedef</phrase> <phrase role="identifier">boost</phrase><phrase role="special">::</phrase><link linkend="boost_typetraits.reference.integral_constant">integral_constant</link><phrase role="special"><</phrase><phrase role="keyword">bool</phrase><phrase role="special">,</phrase> + <phrase role="special">::</phrase><phrase role="identifier">boost</phrase><phrase role="special">::</phrase><link linkend="boost_typetraits.reference.is_reference">is_reference</link><phrase role="special"><</phrase><phrase role="identifier">r1_t</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase> + <phrase role="special">&&</phrase> <phrase role="special">::</phrase><phrase role="identifier">boost</phrase><phrase role="special">::</phrase><link linkend="boost_typetraits.reference.is_reference">is_reference</link><phrase role="special"><</phrase><phrase role="identifier">r2_t</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase> + <phrase role="special">&&</phrase> <phrase role="special">::</phrase><phrase role="identifier">boost</phrase><phrase role="special">::</phrase><link linkend="boost_typetraits.reference.is_same">is_same</link><phrase role="special"><</phrase><phrase role="identifier">r1_t</phrase><phrase role="special">,</phrase> <phrase role="identifier">r2_t</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase><phrase role="special">></phrase> <phrase role="identifier">truth_type</phrase><phrase role="special">;</phrase> + + <phrase role="identifier">detail</phrase><phrase role="special">::</phrase><phrase role="identifier">do_swap</phrase><phrase role="special">(</phrase><phrase role="identifier">one</phrase><phrase role="special">,</phrase> <phrase role="identifier">two</phrase><phrase role="special">,</phrase> <phrase role="identifier">truth_type</phrase><phrase role="special">());</phrase> +<phrase role="special">}</phrase> +</programlisting> + </section> + <section id="boost_typetraits.examples.to_double"> + <title><link linkend="boost_typetraits.examples.to_double"> Convert Numeric + Types and Enums to double</link></title> + <para> + Demonstrates a conversion of <ulink url="../../../../libs/numeric/conversion/doc/html/boost_numericconversion/definitions.html#boost_numericconversion.definitions.numeric_types">Numeric + Types</ulink> and enum types to double: + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase><phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">inline</phrase> <phrase role="keyword">double</phrase> <phrase role="identifier">to_double</phrase><phrase role="special">(</phrase><phrase role="identifier">T</phrase> <phrase role="keyword">const</phrase><phrase role="special">&</phrase> <phrase role="identifier">value</phrase><phrase role="special">)</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <phrase role="keyword">typename</phrase> <phrase role="identifier">boost</phrase><phrase role="special">::</phrase><phrase role="identifier">promote</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase> <phrase role="identifier">promoted</phrase><phrase role="special">;</phrase> + <phrase role="keyword">return</phrase> <phrase role="identifier">boost</phrase><phrase role="special">::</phrase><phrase role="identifier">numeric</phrase><phrase role="special">::</phrase><phrase role="identifier">converter</phrase><phrase role="special"><</phrase><phrase role="keyword">double</phrase><phrase role="special">,</phrase><phrase role="identifier">promoted</phrase><phrase role="special">>::</phrase><phrase role="identifier">convert</phrase><phrase role="special">(</phrase><phrase role="identifier">value</phrase><phrase role="special">);</phrase> +<phrase role="special">}</phrase> +</programlisting> + </section> + </section> + <section id="boost_typetraits.reference"> + <title><link linkend="boost_typetraits.reference"> Alphabetical Reference</link></title> + <section id="boost_typetraits.reference.add_const"><indexterm type="class_name"><primary>Constrained Index Term</primary><secondary>add_const</secondary></indexterm><indexterm><primary>add_const</primary><secondary>Constrained Index Term</secondary></indexterm><indexterm type="class_name"><primary>Constrained Index Term</primary><secondary>add_const</secondary></indexterm><indexterm><primary>add_const</primary><secondary>Constrained Index Term</secondary></indexterm><indexterm type="class_name"><primary>add_const</primary><secondary>add_const</secondary></indexterm><indexterm type="class_name"><primary>Constrained Index Term</primary><secondary>add_const</secondary></indexterm><indexterm><primary>add_const</primary><secondary>Constrained Index Term</secondary></indexterm><indexterm type="class_name"><primary>Constrained Index Term</primary><secondary>add_const</secondary></indexterm><indexterm><primary>add_const</primary><secondary>Constrained Index Term</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.add_const"> add_const</link></title> + <indexterm type="class_name"> + <primary>one</primary> + <secondary>two</secondary> + </indexterm> + + <programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">add_const</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + <emphasis role="bold">type:</emphasis> The same type as <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase> + <phrase role="keyword">const</phrase></computeroutput> for all <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.3. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial specialization of class-templates then this template + will compile, but the member <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">type</phrase></computeroutput> + will always be the same as type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> + except where <link linkend="boost_typetraits.category.transform.broken_compiler_workarounds_">compiler + workarounds</link> have been applied. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">add_const</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <table frame="all"> <title>Examples</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Expression + </para> + </entry><entry> + <para> + Result Type + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_const</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_const</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">&>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">&</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_const</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">*>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">*</phrase> + <phrase role="keyword">const</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_const</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase></computeroutput> + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section id="boost_typetraits.reference.add_cv"><indexterm type="class_name"><primary>add_cv</primary><secondary>add_cv</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.add_cv"> add_cv</link></title> + <indexterm type="class_name"> + <primary>one</primary> + <secondary>two</secondary> + <tertiary>three</tertiary> + </indexterm> + + <programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">add_cv</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + <emphasis role="bold">type:</emphasis> The same type as <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase> + <phrase role="keyword">const</phrase> <phrase role="keyword">volatile</phrase></computeroutput> + for all <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.3. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial specialization of class-templates then this template + will compile, but the member <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">type</phrase></computeroutput> + will always be the same as type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> + except where <link linkend="boost_typetraits.category.transform.broken_compiler_workarounds_">compiler + workarounds</link> have been applied. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">add_cv</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <table frame="all"> <title>Examples</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Expression + </para> + </entry><entry> + <para> + Result Type + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_cv</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase> + <phrase role="keyword">volatile</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_cv</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">&>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">&</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_cv</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">*>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">*</phrase> + <phrase role="keyword">const</phrase> <phrase role="keyword">volatile</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_cv</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase> + <phrase role="keyword">volatile</phrase></computeroutput> + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section id="boost_typetraits.reference.add_pointer"><indexterm type="class_name"><primary>add_pointer</primary><secondary>add_pointer</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.add_pointer"> add_pointer</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">add_pointer</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + <emphasis role="bold">type:</emphasis> The same type as <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_reference</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase><phrase role="special">*</phrase></computeroutput>. + </para> + <para> + The rationale for this template is that it produces the same type as <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">TYPEOF</phrase><phrase role="special">(&</phrase><phrase role="identifier">t</phrase><phrase role="special">)</phrase></computeroutput>, where + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">t</phrase></computeroutput> is an object of type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 8.3.1. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial specialization of class-templates then this template + will compile, but the member <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">type</phrase></computeroutput> + will always be the same as type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> + except where <link linkend="boost_typetraits.category.transform.broken_compiler_workarounds_">compiler + workarounds</link> have been applied. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">add_pointer</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <table frame="all"> <title>Examples</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Expression + </para> + </entry><entry> + <para> + Result Type + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">*</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">&>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">*</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">*>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">**</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">*&>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">**</phrase></computeroutput> + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section id="boost_typetraits.reference.add_reference"><indexterm type="class_name"><primary>add_reference</primary><secondary>add_reference</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.add_reference"> add_reference</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">add_reference</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + <emphasis role="bold">type:</emphasis> If <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> + is not a reference type then <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase><phrase role="special">&</phrase></computeroutput>, otherwise <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 8.3.2. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial specialization of class-templates then this template + will compile, but the member <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">type</phrase></computeroutput> + will always be the same as type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> + except where <link linkend="boost_typetraits.category.transform.broken_compiler_workarounds_">compiler + workarounds</link> have been applied. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">add_reference</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <table frame="all"> <title>Examples</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Expression + </para> + </entry><entry> + <para> + Result Type + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_reference</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">&</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_reference</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">&>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">&</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_reference</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">*>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">*&</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_reference</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">*&>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">*&</phrase></computeroutput> + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section id="boost_typetraits.reference.add_volatile"><indexterm type="class_name"><primary>add_volatile</primary><secondary>add_volatile</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.add_volatile"> add_volatile</link></title> + <indexterm type="class_name"> + <primary>one</primary> + </indexterm> + + <programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">add_volatile</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + <emphasis role="bold">type:</emphasis> The same type as <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase> + <phrase role="keyword">volatile</phrase></computeroutput> for all <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.3. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial specialization of class-templates then this template + will compile, but the member <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">type</phrase></computeroutput> + will always be the same as type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> + except where <link linkend="boost_typetraits.category.transform.broken_compiler_workarounds_">compiler + workarounds</link> have been applied. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">add_volatile</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <table frame="all"> <title>Examples</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Expression + </para> + </entry><entry> + <para> + Result Type + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_volatile</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">volatile</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_volatile</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">&>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">&</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_volatile</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">*>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">*</phrase> + <phrase role="keyword">volatile</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">add_volatile</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase> + <phrase role="keyword">volatile</phrase></computeroutput> + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section id="boost_typetraits.reference.aligned_storage"><indexterm type="class_name"><primary>aligned_storage</primary><secondary>aligned_storage</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.aligned_storage"> aligned_storage</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase> <phrase role="identifier">Size</phrase><phrase role="special">,</phrase> <phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase> <phrase role="identifier">Align</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">aligned_storage</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + <emphasis role="bold">type:</emphasis> a built-in or POD type with size + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">Size</phrase></computeroutput> and an alignment that + is a multiple of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">Align</phrase></computeroutput>. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">aligned_storage</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + </section> + <section id="boost_typetraits.reference.alignment_of"><indexterm type="class_name"><primary>integral_constant</primary><secondary>alignment_of</secondary></indexterm><indexterm><primary>alignment_of</primary><secondary>integral_constant</secondary></indexterm><indexterm type="class_name"><primary>alignment_of</primary><secondary>alignment_of</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.alignment_of"> alignment_of</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">alignment_of</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <link linkend="boost_typetraits.reference.integral_constant">integral_constant</link><phrase role="special"><</phrase><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase><phrase role="special">,</phrase> <phrase role="identifier">ALIGNOF</phrase><phrase role="special">(</phrase><phrase role="identifier">T</phrase><phrase role="special">)></phrase> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> Class template alignment<emphasis role="underline">of inherits from `</emphasis>_integral_constant<std::size_t, + ALIGNOF(T)><computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="special">,</phrase> <phrase role="identifier">where</phrase> + </computeroutput>ALIGNOF(T)` is the alignment of type T. + </para> + <para> + <emphasis>Note: strictly speaking you should only rely on the value of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">ALIGNOF</phrase><phrase role="special">(</phrase><phrase role="identifier">T</phrase><phrase role="special">)</phrase></computeroutput> being + a multiple of the true alignment of T, although in practice it does compute + the correct value in all the cases we know about.</emphasis> + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">alignment_of</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">alignment_of</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">integral_constant</link><phrase role="special"><</phrase><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase><phrase role="special">,</phrase> <phrase role="identifier">ALIGNOF</phrase><phrase role="special">(</phrase><phrase role="keyword">int</phrase><phrase role="special">)></phrase></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">alignment_of</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">integral_constant</link><phrase role="special"><</phrase><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase><phrase role="special">,</phrase> <phrase role="identifier">ALIGNOF</phrase><phrase role="special">(</phrase><phrase role="keyword">char</phrase><phrase role="special">)></phrase></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">alignment_of</phrase><phrase role="special"><</phrase><phrase role="keyword">double</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + with value <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">ALIGNOF</phrase><phrase role="special">(</phrase><phrase role="keyword">double</phrase><phrase role="special">)</phrase></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">alignment_of</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.decay"><indexterm type="class_name"><primary>decay</primary><secondary>decay</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.decay"> decay</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">decay</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + <emphasis role="bold">type:</emphasis> Let <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">U</phrase></computeroutput> + be the result of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_reference</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput>, then if <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">U</phrase></computeroutput> + is an array type, the result is <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_extent</phrase><phrase role="special"><</phrase><phrase role="identifier">U</phrase><phrase role="special">>*</phrase></computeroutput>, + otherwise if <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">U</phrase></computeroutput> is a function + type then the result is <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">U</phrase><phrase role="special">*</phrase></computeroutput>, otherwise the result is <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">U</phrase></computeroutput>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.1. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">decay</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <table frame="all"> <title>Examples</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Expression + </para> + </entry><entry> + <para> + Result Type + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">decay</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">[</phrase><phrase role="number">2</phrase><phrase role="special">][</phrase><phrase role="number">3</phrase><phrase role="special">]>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">[</phrase><phrase role="number">2</phrase><phrase role="special">]*</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">decay</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">(&)[</phrase><phrase role="number">2</phrase><phrase role="special">]>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">*</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">decay</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">(&)(</phrase><phrase role="keyword">double</phrase><phrase role="special">)>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">(*)(</phrase><phrase role="keyword">double</phrase><phrase role="special">)</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">(*)(</phrase><phrase role="keyword">double</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">(*)(</phrase><phrase role="keyword">double</phrase><phrase role="special">)</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">(</phrase><phrase role="keyword">double</phrase><phrase role="special">)</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">(*)(</phrase><phrase role="keyword">double</phrase><phrase role="special">)</phrase></computeroutput> + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section id="boost_typetraits.reference.extent"><indexterm type="class_name"><primary>integral_constant</primary><secondary>extent</secondary></indexterm><indexterm><primary>extent</primary><secondary>integral_constant</secondary></indexterm><indexterm type="class_name"><primary>extent</primary><secondary>extent</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.extent"> extent</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">,</phrase> <phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase> <phrase role="identifier">N</phrase> <phrase role="special">=</phrase> <phrase role="number">0</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">extent</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <link linkend="boost_typetraits.reference.integral_constant">integral_constant</link><phrase role="special"><</phrase><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase><phrase role="special">,</phrase> <phrase role="identifier">EXTENT</phrase><phrase role="special">(</phrase><phrase role="identifier">T</phrase><phrase role="special">,</phrase><phrase role="identifier">N</phrase><phrase role="special">)></phrase> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> Class template extent inherits + from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">integral_constant</link><phrase role="special"><</phrase><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase><phrase role="special">,</phrase> <phrase role="identifier">EXTENT</phrase><phrase role="special">(</phrase><phrase role="identifier">T</phrase><phrase role="special">,</phrase><phrase role="identifier">N</phrase><phrase role="special">)></phrase></computeroutput>, + where <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">EXTENT</phrase><phrase role="special">(</phrase><phrase role="identifier">T</phrase><phrase role="special">,</phrase><phrase role="identifier">N</phrase><phrase role="special">)</phrase></computeroutput> is the number of elements in the N'th array + dimention of type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput>. + </para> + <para> + If <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> is not an array type, + or if <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">N</phrase> <phrase role="special">></phrase> + <link linkend="boost_typetraits.reference.rank">rank</link><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput>, or if the N'th array bound is incomplete, + then <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">EXTENT</phrase><phrase role="special">(</phrase><phrase role="identifier">T</phrase><phrase role="special">,</phrase><phrase role="identifier">N</phrase><phrase role="special">)</phrase></computeroutput> is zero. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">extent</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">extent</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">[</phrase><phrase role="number">1</phrase><phrase role="special">]></phrase></computeroutput> inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">integral_constant</link><phrase role="special"><</phrase><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase><phrase role="special">,</phrase> <phrase role="number">1</phrase><phrase role="special">></phrase></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">extent</phrase><phrase role="special"><</phrase><phrase role="keyword">double</phrase><phrase role="special">[</phrase><phrase role="number">2</phrase><phrase role="special">][</phrase><phrase role="number">3</phrase><phrase role="special">][</phrase><phrase role="number">4</phrase><phrase role="special">],</phrase> + <phrase role="number">1</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">integral_constant</link><phrase role="special"><</phrase><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase><phrase role="special">,</phrase> <phrase role="number">3</phrase><phrase role="special">></phrase></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">extent</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">[</phrase><phrase role="number">4</phrase><phrase role="special">]>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>4</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">extent</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">[][</phrase><phrase role="number">2</phrase><phrase role="special">]>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>0</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">extent</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">[][</phrase><phrase role="number">2</phrase><phrase role="special">],</phrase> <phrase role="number">1</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>2</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">extent</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">*>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>0</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">extent</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.floating_point_promotion"><indexterm type="class_name"><primary>floating_point_promotion</primary><secondary>floating_point_promotion</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.floating_point_promotion"> + floating_point_promotion</link></title> +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">floating_point_promotion</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + <emphasis role="bold">type:</emphasis> If floating point promotion can be + applied to an rvalue of type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput>, + then applies floating point promotion to <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> + and keeps cv-qualifiers of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput>, + otherwise leaves <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> unchanged. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 4.6. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">floating_point_promotion</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <table frame="all"> <title>Examples</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Expression + </para> + </entry><entry> + <para> + Result Type + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">floating_point_promotion</phrase><phrase role="special"><</phrase><phrase role="keyword">float</phrase> + <phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">double</phrase> <phrase role="keyword">const</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">floating_point_promotion</phrase><phrase role="special"><</phrase><phrase role="keyword">float</phrase><phrase role="special">&>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">float</phrase><phrase role="special">&</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">floating_point_promotion</phrase><phrase role="special"><</phrase><phrase role="keyword">short</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">short</phrase></computeroutput> + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section id="boost_typetraits.reference.function_traits"><indexterm type="typedef_name"><primary>result_type</primary><secondary>function_traits</secondary></indexterm><indexterm><primary>function_traits</primary><secondary>result_type</secondary></indexterm><indexterm type="class_name"><primary>function_traits</primary><secondary>function_traits</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.function_traits"> function_traits</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">F</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">function_traits</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">static</phrase> <phrase role="keyword">const</phrase> <phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase> <phrase role="identifier">arity</phrase> <phrase role="special">=</phrase> <replaceable>see-below</replaceable><phrase role="special">;</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">result_type</phrase><phrase role="special">;</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> arg<replaceable>N</replaceable>_type<phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + The class template function_traits will only compile if: + </para> + <itemizedlist> + <listitem> + The compiler supports partial specialization of class templates. + </listitem> + <listitem> + The template argument <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">F</phrase></computeroutput> + is a <emphasis>function type</emphasis>, note that this <emphasis><emphasis role="bold">is not</emphasis></emphasis> the same thing as a <emphasis>pointer + to a function</emphasis>. + </listitem> + </itemizedlist> + <tip> + <para> + function_traits is intended to introspect only C++ functions of the form + R (), R( A1 ), R ( A1, ... etc. ) and not function pointers or class member + functions. To convert a function pointer type to a suitable type use <link linkend="boost_typetraits.reference.remove_pointer">remove_pointer</link>. + </para> + </tip> + <table frame="all"> <title>Function Traits Members</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Member + </para> + </entry><entry> + <para> + Description + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">function_traits</phrase><phrase role="special"><</phrase><phrase role="identifier">F</phrase><phrase role="special">>::</phrase><phrase role="identifier">arity</phrase></computeroutput> + </para> + </entry><entry> + <para> + An integral constant expression that gives the number of arguments + accepted by the function type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">F</phrase></computeroutput>. + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">function_traits</phrase><phrase role="special"><</phrase><phrase role="identifier">F</phrase><phrase role="special">>::</phrase><phrase role="identifier">result_type</phrase></computeroutput> + </para> + </entry><entry> + <para> + The type returned by function type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">F</phrase></computeroutput>. + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">function_traits</phrase><phrase role="special"><</phrase><phrase role="identifier">F</phrase><phrase role="special">>::</phrase>arg<replaceable>N</replaceable>_type</computeroutput> + </para> + </entry><entry> + <para> + The <replaceable>N</replaceable>th argument type of function type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">F</phrase></computeroutput>, + where <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="number">1</phrase> <phrase role="special"><=</phrase> + <phrase role="identifier">N</phrase> <phrase role="special"><=</phrase> + <phrase role="identifier">arity</phrase></computeroutput> of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">F</phrase></computeroutput>. + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> <table frame="all"> <title>Examples</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Expression + </para> + </entry><entry> + <para> + Result + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">function_traits</phrase><phrase role="special"><</phrase><phrase role="keyword">void</phrase> <phrase role="special">(</phrase><phrase role="keyword">void</phrase><phrase role="special">)>::</phrase><phrase role="identifier">arity</phrase></computeroutput> + </para> + </entry><entry> + <para> + An integral constant expression that has the value 0. + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">function_traits</phrase><phrase role="special"><</phrase><phrase role="keyword">long</phrase> <phrase role="special">(</phrase><phrase role="keyword">int</phrase><phrase role="special">)>::</phrase><phrase role="identifier">arity</phrase></computeroutput> + </para> + </entry><entry> + <para> + An integral constant expression that has the value 1. + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">function_traits</phrase><phrase role="special"><</phrase><phrase role="keyword">long</phrase> <phrase role="special">(</phrase><phrase role="keyword">int</phrase><phrase role="special">,</phrase> <phrase role="keyword">long</phrase><phrase role="special">,</phrase> <phrase role="keyword">double</phrase><phrase role="special">,</phrase> <phrase role="keyword">void</phrase><phrase role="special">*)>::</phrase><phrase role="identifier">arity</phrase></computeroutput> + </para> + </entry><entry> + <para> + An integral constant expression that has the value 4. + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">function_traits</phrase><phrase role="special"><</phrase><phrase role="keyword">void</phrase> <phrase role="special">(</phrase><phrase role="keyword">void</phrase><phrase role="special">)>::</phrase><phrase role="identifier">result_type</phrase></computeroutput> + </para> + </entry><entry> + <para> + The type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">void</phrase></computeroutput>. + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">function_traits</phrase><phrase role="special"><</phrase><phrase role="keyword">long</phrase> <phrase role="special">(</phrase><phrase role="keyword">int</phrase><phrase role="special">)>::</phrase><phrase role="identifier">result_type</phrase></computeroutput> + </para> + </entry><entry> + <para> + The type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">long</phrase></computeroutput>. + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">function_traits</phrase><phrase role="special"><</phrase><phrase role="keyword">long</phrase> <phrase role="special">(</phrase><phrase role="keyword">int</phrase><phrase role="special">)>::</phrase><phrase role="identifier">arg1_type</phrase></computeroutput> + </para> + </entry><entry> + <para> + The type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase></computeroutput>. + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">function_traits</phrase><phrase role="special"><</phrase><phrase role="keyword">long</phrase> <phrase role="special">(</phrase><phrase role="keyword">int</phrase><phrase role="special">,</phrase> <phrase role="keyword">long</phrase><phrase role="special">,</phrase> <phrase role="keyword">double</phrase><phrase role="special">,</phrase> <phrase role="keyword">void</phrase><phrase role="special">*)>::</phrase><phrase role="identifier">arg4_type</phrase></computeroutput> + </para> + </entry><entry> + <para> + The type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">void</phrase><phrase role="special">*</phrase></computeroutput>. + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">function_traits</phrase><phrase role="special"><</phrase><phrase role="keyword">long</phrase> <phrase role="special">(</phrase><phrase role="keyword">int</phrase><phrase role="special">,</phrase> <phrase role="keyword">long</phrase><phrase role="special">,</phrase> <phrase role="keyword">double</phrase><phrase role="special">,</phrase> <phrase role="keyword">void</phrase><phrase role="special">*)>::</phrase><phrase role="identifier">arg5_type</phrase></computeroutput> + </para> + </entry><entry> + <para> + A compiler error: there is no <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">arg5_type</phrase></computeroutput> + since there are only four arguments. + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">function_traits</phrase><phrase role="special"><</phrase><phrase role="keyword">long</phrase> <phrase role="special">(*)(</phrase><phrase role="keyword">void</phrase><phrase role="special">)>::</phrase><phrase role="identifier">arity</phrase></computeroutput> + </para> + </entry><entry> + <para> + A compiler error: argument type is a <emphasis>function pointer</emphasis>, + and not a <emphasis>function type</emphasis>. + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section id="boost_typetraits.reference.has_nothrow_assign"><indexterm type="class_name"><primary>has_nothrow_assign</primary><secondary>has_nothrow_assign</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.has_nothrow_assign"> has_nothrow_assign</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">has_nothrow_assign</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + type with a non-throwing assignment-operator then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + Type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> must be a complete + type. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial-specialization of class templates, then this template + can not be used with function types. + </para> + <para> + Without some (as yet unspecified) help from the compiler, <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_nothrow_assign</phrase></computeroutput> + will never report that a class or struct has a non-throwing assignment-operator; + this is always safe, if possibly sub-optimal. Currently (May 2005) only Visual + C++ 8 has the necessary compiler support to ensure that this trait "just + works". + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">has_nothrow_assign</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + </section> + <section id="boost_typetraits.reference.has_nothrow_constructor"><indexterm type="class_name"><primary>has_nothrow_default_constructor</primary><secondary>has_nothrow_constructor</secondary></indexterm><indexterm><primary>has_nothrow_constructor</primary><secondary>has_nothrow_default_constructor</secondary></indexterm><indexterm type="class_name"><primary>has_nothrow_constructor</primary><secondary>has_nothrow_constructor</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.has_nothrow_constructor"> + has_nothrow_constructor</link></title> +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">has_nothrow_constructor</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">has_nothrow_default_constructor</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + type with a non-throwing default-constructor then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + Type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> must be a complete + type. + </para> + <para> + These two traits are synonyms for each other. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial-specialization of class templates, then this template + can not be used with function types. + </para> + <para> + Without some (as yet unspecified) help from the compiler, <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_nothrow_constructor</phrase></computeroutput> + will never report that a class or struct has a non-throwing default-constructor; + this is always safe, if possibly sub-optimal. Currently (May 2005) only Visual + C++ 8 has the necessary compiler <link linkend="boost_typetraits.intrinsics">intrinsics</link> + to ensure that this trait "just works". + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">has_nothrow_constructor</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + </section> + <section id="boost_typetraits.reference.has_nothrow_copy"><indexterm type="class_name"><primary>has_nothrow_copy_constructor</primary><secondary>has_nothrow_copy</secondary></indexterm><indexterm><primary>has_nothrow_copy</primary><secondary>has_nothrow_copy_constructor</secondary></indexterm><indexterm type="class_name"><primary>has_nothrow_copy</primary><secondary>has_nothrow_copy</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.has_nothrow_copy"> has_nothrow_copy</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">has_nothrow_copy</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">has_nothrow_copy_constructor</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + type with a non-throwing copy-constructor then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + Type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> must be a complete + type. + </para> + <para> + These two traits are synonyms for each other. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial-specialization of class templates, then this template + can not be used with function types. + </para> + <para> + Without some (as yet unspecified) help from the compiler, <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_nothrow_copy</phrase></computeroutput> + will never report that a class or struct has a non-throwing copy-constructor; + this is always safe, if possibly sub-optimal. Currently (May 2005) only Visual + C++ 8 has the necessary compiler <link linkend="boost_typetraits.intrinsics">intrinsics</link> + to ensure that this trait "just works". + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">has_nothrow_copy</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + </section> + <section id="boost_typetraits.reference.has_nothrow_cp_cons"> + <title><link linkend="boost_typetraits.reference.has_nothrow_cp_cons"> has_nothrow_copy_constructor</link></title> + <para> + See <link linkend="boost_typetraits.reference.has_nothrow_copy">has_nothrow_copy</link>. + </para> + </section> + <section id="boost_typetraits.reference.has_no_throw_def_cons"> + <title><link linkend="boost_typetraits.reference.has_no_throw_def_cons"> has_nothrow_default_constructor</link></title> + <para> + See <link linkend="boost_typetraits.reference.has_nothrow_constructor">has_nothrow_constructor</link>. + </para> + </section> + <section id="boost_typetraits.reference.has_trivial_assign"><indexterm type="class_name"><primary>has_trivial_assign</primary><secondary>has_trivial_assign</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.has_trivial_assign"> has_trivial_assign</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">has_trivial_assign</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + type with a trivial assignment-operator then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + If a type has a trivial assignment-operator then the operator has the same + effect as copying the bits of one object to the other: calls to the operator + can be safely replaced with a call to <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">memcpy</phrase></computeroutput>. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial-specialization of class templates, then this template + can not be used with function types. + </para> + <para> + Without some (as yet unspecified) help from the compiler, has_trivial_assign + will never report that a user-defined class or struct has a trivial constructor; + this is always safe, if possibly sub-optimal. Currently (May 2005) only MWCW + 9 and Visual C++ 8 have the necessary compiler <link linkend="boost_typetraits.intrinsics">intrinsics</link> + to detect user-defined classes with trivial constructors. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 12.8p11. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">has_trivial_assign</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_assign</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_assign</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase><phrase role="special">*>::</phrase><phrase role="identifier">type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_assign</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(*)(</phrase><phrase role="keyword">long</phrase><phrase role="special">)>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_assign</phrase><phrase role="special"><</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_assign</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.has_trivial_constructor"><indexterm type="class_name"><primary>has_trivial_default_constructor</primary><secondary>has_trivial_constructor</secondary></indexterm><indexterm><primary>has_trivial_constructor</primary><secondary>has_trivial_default_constructor</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.has_trivial_constructor"> + has_trivial_constructor</link></title> +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">has_trivial_constructor</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">has_trivial_default_constructor</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + type with a trivial default-constructor then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + These two traits are synonyms for each other. + </para> + <para> + If a type has a trivial default-constructor then the constructor have no + effect: calls to the constructor can be safely omitted. Note that using meta-programming + to omit a call to a single trivial-constructor call is of no benefit whatsoever. + However, if loops and/or exception handling code can also be omitted, then + some benefit in terms of code size and speed can be obtained. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial-specialization of class templates, then this template + can not be used with function types. + </para> + <para> + Without some (as yet unspecified) help from the compiler, has_trivial_constructor + will never report that a user-defined class or struct has a trivial constructor; + this is always safe, if possibly sub-optimal. Currently (May 2005) only MWCW + 9 and Visual C++ 8 have the necessary compiler <link linkend="boost_typetraits.intrinsics">intrinsics</link> + to detect user-defined classes with trivial constructors. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 12.1p6. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">has_trivial_constructor</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_constructor</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">></phrase></computeroutput> inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_constructor</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase><phrase role="special">*>::</phrase><phrase role="identifier">type</phrase></computeroutput> + is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_constructor</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(*)(</phrase><phrase role="keyword">long</phrase><phrase role="special">)>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_constructor</phrase><phrase role="special"><</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_constructor</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> + is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.has_trivial_copy"><indexterm type="class_name"><primary>has_trivial_copy_constructor</primary><secondary>has_trivial_copy</secondary></indexterm><indexterm><primary>has_trivial_copy</primary><secondary>has_trivial_copy_constructor</secondary></indexterm><indexterm type="class_name"><primary>has_trivial_copy</primary><secondary>has_trivial_copy</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.has_trivial_copy"> has_trivial_copy</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">has_trivial_copy</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> + +<phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">has_trivial_copy_constructor</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + type with a trivial copy-constructor then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + These two traits are synonyms for each other. + </para> + <para> + If a type has a trivial copy-constructor then the constructor has the same + effect as copying the bits of one object to the other: calls to the constructor + can be safely replaced with a call to <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">memcpy</phrase></computeroutput>. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial-specialization of class templates, then this template + can not be used with function types. + </para> + <para> + Without some (as yet unspecified) help from the compiler, has_trivial_copy + will never report that a user-defined class or struct has a trivial constructor; + this is always safe, if possibly sub-optimal. Currently (May 2005) only MWCW + 9 and Visual C++ 8 have the necessary compiler <link linkend="boost_typetraits.intrinsics">intrinsics</link> + to detect user-defined classes with trivial constructors. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 12.8p6. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">has_trivial_copy</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_copy</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_copy</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase><phrase role="special">*>::</phrase><phrase role="identifier">type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_copy</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(*)(</phrase><phrase role="keyword">long</phrase><phrase role="special">)>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_copy</phrase><phrase role="special"><</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_copy</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.has_trivial_cp_cons"> + <title><link linkend="boost_typetraits.reference.has_trivial_cp_cons"> has_trivial_copy_constructor</link></title> + <para> + See <link linkend="boost_typetraits.reference.has_trivial_copy">has_trivial_copy</link>. + </para> + </section> + <section id="boost_typetraits.reference.has_trivial_def_cons"> + <title><link linkend="boost_typetraits.reference.has_trivial_def_cons"> has_trivial_default_constructor</link></title> + <para> + See <link linkend="boost_typetraits.reference.has_trivial_constructor">has_trivial_constructor</link>. + </para> + </section> + <section id="boost_typetraits.reference.has_trivial_destructor"><indexterm type="class_name"><primary>has_trivial_destructor</primary><secondary>has_trivial_destructor</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.has_trivial_destructor"> has_trivial_destructor</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">has_trivial_destructor</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + type with a trivial destructor then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + If a type has a trivial destructor then the destructor has no effect: calls + to the destructor can be safely omitted. Note that using meta-programming + to omit a call to a single trivial-constructor call is of no benefit whatsoever. + However, if loops and/or exception handling code can also be omitted, then + some benefit in terms of code size and speed can be obtained. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial-specialization of class templates, then this template + can not be used with function types. + </para> + <para> + Without some (as yet unspecified) help from the compiler, has_trivial_destructor + will never report that a user-defined class or struct has a trivial destructor; + this is always safe, if possibly sub-optimal. Currently (May 2005) only MWCW + 9 and Visual C++ 8 have the necessary compiler <link linkend="boost_typetraits.intrinsics">intrinsics</link> + to detect user-defined classes with trivial constructors. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 12.4p3. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">has_trivial_destructor</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_destructor</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">></phrase></computeroutput> inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_destructor</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase><phrase role="special">*>::</phrase><phrase role="identifier">type</phrase></computeroutput> + is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_destructor</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(*)(</phrase><phrase role="keyword">long</phrase><phrase role="special">)>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_destructor</phrase><phrase role="special"><</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">has_trivial_destructor</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> + is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.has_virtual_destructor"><indexterm type="class_name"><primary>has_virtual_destructor</primary><secondary>has_virtual_destructor</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.has_virtual_destructor"> has_virtual_destructor</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">has_virtual_destructor</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + type with a virtual destructor then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> This trait is provided + for completeness, since it's part of the Technical Report on C++ Library + Extensions. However, there is currently no way to portably implement this + trait. The default version provided always inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>, + and has to be explicitly specialized for types with virtual destructors unless + the compiler used has compiler <link linkend="boost_typetraits.intrinsics">intrinsics</link> + that enable the trait to do the right thing: currently (May 2005) only Visual + C++ 8 and GCC-4.3 have the necessary <link linkend="boost_typetraits.intrinsics">intrinsics</link>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 12.4. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">has_virtual_destructor</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + </section> + <section id="boost_typetraits.reference.integral_constant"><indexterm type="typedef_name"><primary>value_type</primary><secondary>integral_constant</secondary></indexterm><indexterm><primary>integral_constant</primary><secondary>value_type</secondary></indexterm><indexterm type="typedef_name"><primary>true_type</primary><secondary>integral_constant</secondary></indexterm><indexterm><primary>integral_constant</primary><secondary>true_type</secondary></indexterm><indexterm type="class_name"><primary>integral_constant</primary><secondary>integral_constant</secondary></indexterm><indexterm type="typedef_name"><primary>false_type</primary><secondary>integral_constant</secondary></indexterm><indexterm><primary>integral_constant</primary><secondary>false_type</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.integral_constant"> integral_constant</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">,</phrase> <phrase role="identifier">T</phrase> <phrase role="identifier">val</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">integral_constant</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <phrase role="identifier">integral_constant</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">,</phrase> <phrase role="identifier">val</phrase><phrase role="special">></phrase> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> + <phrase role="keyword">typedef</phrase> <phrase role="identifier">T</phrase> <phrase role="identifier">value_type</phrase><phrase role="special">;</phrase> + <phrase role="keyword">static</phrase> <phrase role="keyword">const</phrase> <phrase role="identifier">T</phrase> <phrase role="identifier">value</phrase> <phrase role="special">=</phrase> <phrase role="identifier">val</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> + +<phrase role="keyword">typedef</phrase> <phrase role="identifier">integral_constant</phrase><phrase role="special"><</phrase><phrase role="keyword">bool</phrase><phrase role="special">,</phrase> <phrase role="keyword">true</phrase><phrase role="special">></phrase> <phrase role="identifier">true_type</phrase><phrase role="special">;</phrase> +<phrase role="keyword">typedef</phrase> <phrase role="identifier">integral_constant</phrase><phrase role="special"><</phrase><phrase role="keyword">bool</phrase><phrase role="special">,</phrase> <phrase role="keyword">false</phrase><phrase role="special">></phrase> <phrase role="identifier">false_type</phrase><phrase role="special">;</phrase> +</programlisting> + <para> + Class template <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">integral_constant</phrase></computeroutput> + is the common base class for all the value-based type traits. The two typedef's + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">true_type</phrase></computeroutput> and <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">false_type</phrase></computeroutput> are provided for convenience: + most of the value traits are Boolean properties and so will inherit from + one of these. + </para> + </section> + <section id="boost_typetraits.reference.integral_promotion"><indexterm type="class_name"><primary>integral_promotion</primary><secondary>integral_promotion</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.integral_promotion"> integral_promotion</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">integral_promotion</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + <emphasis role="bold">type:</emphasis> If integral promotion can be applied + to an rvalue of type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput>, then + applies integral promotion to <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> + and keeps cv-qualifiers of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput>, + otherwise leaves <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> unchanged. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 4.5 except 4.5/3 + (integral bit-field). + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">integral_promotion</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <table frame="all"> <title>Examples</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Expression + </para> + </entry><entry> + <para> + Result Type + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">integral_promotion</phrase><phrase role="special"><</phrase><phrase role="keyword">short</phrase> + <phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">integral_promotion</phrase><phrase role="special"><</phrase><phrase role="keyword">short</phrase><phrase role="special">&>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">short</phrase><phrase role="special">&</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">integral_promotion</phrase><phrase role="special"><</phrase><phrase role="keyword">enum</phrase> <phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">float_round_style</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase></computeroutput> + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section id="boost_typetraits.reference.is_abstract"><indexterm type="class_name"><primary>is_abstract</primary><secondary>is_abstract</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_abstract"> is_abstract</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_abstract</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + abstract type then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 10.3. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_abstract</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> The compiler must + support DR337 (as of April 2005: GCC 3.4, VC++ 7.1 (and later), Intel C++ + 7 (and later), and Comeau 4.3.2). Otherwise behaves the same as <link linkend="boost_typetraits.reference.is_polymorphic">is_polymorphic</link>; + this is the "safe fallback position" for which polymorphic types + are always regarded as potentially abstract. The macro BOOST_NO_IS_ABSTRACT + is used to signify that the implementation is buggy, users should check for + this in their own code if the "safe fallback" is not suitable for + their particular use-case. + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + Given: <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">class</phrase> <phrase role="identifier">abc</phrase><phrase role="special">{</phrase> <phrase role="keyword">virtual</phrase> <phrase role="special">~</phrase><phrase role="identifier">abc</phrase><phrase role="special">()</phrase> <phrase role="special">=</phrase> <phrase role="number">0</phrase><phrase role="special">;</phrase> <phrase role="special">};</phrase></computeroutput> + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_abstract</phrase><phrase role="special"><</phrase><phrase role="identifier">abc</phrase><phrase role="special">></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_abstract</phrase><phrase role="special"><</phrase><phrase role="identifier">abc</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_abstract</phrase><phrase role="special"><</phrase><phrase role="identifier">abc</phrase> <phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_abstract</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_arithmetic"><indexterm type="class_name"><primary>is_arithmetic</primary><secondary>is_arithmetic</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_arithmetic"> is_arithmetic</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_arithmetic</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + arithmetic type then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + Arithmetic types include integral and floating point types (see also <link linkend="boost_typetraits.reference.is_integral">is_integral</link> and + <link linkend="boost_typetraits.reference.is_floating_point">is_floating_point</link>). + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.1p8. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_arithmetic</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_arithmetic</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_arithmetic</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_arithmetic</phrase><phrase role="special"><</phrase><phrase role="keyword">double</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_arithmetic</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_array"><indexterm type="class_name"><primary>is_array</primary><secondary>is_array</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_array"> is_array</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_array</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + array type then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.2 and 8.3.4. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_array</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial-specialization of class templates, then this template + can give the wrong result with function types. + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_array</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">[</phrase><phrase role="number">2</phrase><phrase role="special">]></phrase></computeroutput> inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_array</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase><phrase role="special">[</phrase><phrase role="number">2</phrase><phrase role="special">][</phrase><phrase role="number">3</phrase><phrase role="special">]>::</phrase><phrase role="identifier">type</phrase></computeroutput> + is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_array</phrase><phrase role="special"><</phrase><phrase role="keyword">double</phrase><phrase role="special">[]>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_array</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_base_of"><indexterm type="class_name"><primary>is_base_of</primary><secondary>is_base_of</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_base_of"> is_base_of</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">Base</phrase><phrase role="special">,</phrase> <phrase role="keyword">class</phrase> <phrase role="identifier">Derived</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_base_of</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If Base is base class of type + Derived or if both types are the same then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + This template will detect non-public base classes, and ambiguous base classes. + </para> + <para> + Note that <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_base_of</phrase><phrase role="special"><</phrase><phrase role="identifier">X</phrase><phrase role="special">,</phrase><phrase role="identifier">X</phrase><phrase role="special">></phrase></computeroutput> will always inherit from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>. + <emphasis role="bold">This is the case even if <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">X</phrase></computeroutput> + is not a class type</emphasis>. This is a change in behaviour from Boost-1.33 + in order to track the Technical Report on C++ Library Extensions. + </para> + <para> + Types <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">Base</phrase></computeroutput> and <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">Derived</phrase></computeroutput> must not be incomplete types. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 10. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_base_of</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial-specialization of class templates, then this template + can not be used with function types. There are some older compilers which + will produce compiler errors if <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">Base</phrase></computeroutput> + is a private base class of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">Derived</phrase></computeroutput>, + or if <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">Base</phrase></computeroutput> is an ambiguous + base of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">Derived</phrase></computeroutput>. These compilers + include Borland C++, older versions of Sun Forte C++, Digital Mars C++, and + older versions of EDG based compilers. + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + Given: <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="keyword">class</phrase> <phrase role="identifier">Base</phrase><phrase role="special">{};</phrase> <phrase role="keyword">class</phrase> <phrase role="identifier">Derived</phrase> <phrase role="special">:</phrase> + <phrase role="keyword">public</phrase> <phrase role="identifier">Base</phrase><phrase role="special">{};</phrase></computeroutput> + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_base_of</phrase><phrase role="special"><</phrase><phrase role="identifier">Base</phrase><phrase role="special">,</phrase> <phrase role="identifier">Derived</phrase><phrase role="special">></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_base_of</phrase><phrase role="special"><</phrase><phrase role="identifier">Base</phrase><phrase role="special">,</phrase> <phrase role="identifier">Derived</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_base_of</phrase><phrase role="special"><</phrase><phrase role="identifier">Base</phrase><phrase role="special">,</phrase> <phrase role="identifier">Derived</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_base_of</phrase><phrase role="special"><</phrase><phrase role="identifier">Base</phrase><phrase role="special">,</phrase> <phrase role="identifier">Derived</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_base_of</phrase><phrase role="special"><</phrase><phrase role="identifier">Base</phrase><phrase role="special">,</phrase> <phrase role="identifier">Base</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>: a class is regarded as it's + own base. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_base_of</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_class"><indexterm type="class_name"><primary>is_class</primary><secondary>is_class</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_class"> is_class</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_class</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + class type then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.2 and 9.2. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_class</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> Without (some as + yet unspecified) help from the compiler, we cannot distinguish between union + and class types, as a result this type will erroneously inherit from <link linkend="boost_typetraits.reference.integral_constant">true_type</link> for + union types. See also <link linkend="boost_typetraits.reference.is_union">is_union</link>. + Currently (May 2005) only Visual C++ 8 has the necessary compiler <link linkend="boost_typetraits.intrinsics">intrinsics</link> + to correctly identify union types, and therefore make is_class function correctly. + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + Given: <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">class</phrase> <phrase role="identifier">MyClass</phrase><phrase role="special">;</phrase></computeroutput> then: + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_class</phrase><phrase role="special"><</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_class</phrase><phrase role="special"><</phrase><phrase role="identifier">MyClass</phrase> <phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_class</phrase><phrase role="special"><</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_class</phrase><phrase role="special"><</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">&>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_class</phrase><phrase role="special"><</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">*>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_class</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_complex"><indexterm type="class_name"><primary>is_complex</primary><secondary>is_complex</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_complex"> is_complex</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_complex</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> + is a complex number type then true (of type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">complex</phrase><phrase role="special"><</phrase><phrase role="identifier">U</phrase><phrase role="special">></phrase></computeroutput> + for some type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">U</phrase></computeroutput>), otherwise + false. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 26.2. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_complex</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + </section> + <section id="boost_typetraits.reference.is_compound"><indexterm type="class_name"><primary>is_compound</primary><secondary>is_compound</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_compound"> is_compound</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_compound</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + compound type then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + Any type that is not a fundamental type is a compound type (see also <link linkend="boost_typetraits.reference.is_fundamental">is_fundamental</link>). + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.2. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_compound</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_compound</phrase><phrase role="special"><</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_compound</phrase><phrase role="special"><</phrase><phrase role="identifier">MyEnum</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_compound</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">*>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_compound</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">&>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_compound</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_compound</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_const"><indexterm type="class_name"><primary>is_const</primary><secondary>is_const</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_const"> is_const</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_const</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (top level) const-qualified + type then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.3. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_const</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_const</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">></phrase></computeroutput> inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_const</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase> <phrase role="keyword">volatile</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_const</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">*</phrase> <phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_const</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">*>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>false</emphasis>: + the const-qualifier is not at the top level in this case. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_const</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">&>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>false</emphasis>: + the const-qualifier is not at the top level in this case. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_const</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_const</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_convertible"><indexterm type="class_name"><primary>is_convertible</primary><secondary>is_convertible</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_convertible"> is_convertible</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">From</phrase><phrase role="special">,</phrase> <phrase role="keyword">class</phrase> <phrase role="identifier">To</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_convertible</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If an imaginary lvalue of type + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">From</phrase></computeroutput> is convertible to type + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">To</phrase></computeroutput> then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + Type From must not be an incomplete type. + </para> + <para> + Type To must not be an incomplete, or function type. + </para> + <para> + No types are considered to be convertible to array types or abstract-class + types. + </para> + <para> + This template can not detect whether a converting-constructor is <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">public</phrase></computeroutput> or not: if type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">To</phrase></computeroutput> + has a <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">private</phrase></computeroutput> converting constructor + from type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">From</phrase></computeroutput> then instantiating + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_convertible</phrase><phrase role="special"><</phrase><phrase role="identifier">From</phrase><phrase role="special">,</phrase> <phrase role="identifier">To</phrase><phrase role="special">></phrase></computeroutput> + will produce a compiler error. For this reason <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_convertible</phrase></computeroutput> + can not be used to determine whether a type has a <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">public</phrase></computeroutput> + copy-constructor or not. + </para> + <para> + This template will also produce compiler errors if the conversion is ambiguous, + for example: + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">struct</phrase> <phrase role="identifier">A</phrase> <phrase role="special">{};</phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">B</phrase> <phrase role="special">:</phrase> <phrase role="identifier">A</phrase> <phrase role="special">{};</phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">C</phrase> <phrase role="special">:</phrase> <phrase role="identifier">A</phrase> <phrase role="special">{};</phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">D</phrase> <phrase role="special">:</phrase> <phrase role="identifier">B</phrase><phrase role="special">,</phrase> <phrase role="identifier">C</phrase> <phrase role="special">{};</phrase> +<phrase role="comment">// This produces a compiler error, the conversion is ambiguous: +</phrase><phrase role="keyword">bool</phrase> <phrase role="keyword">const</phrase> <phrase role="identifier">y</phrase> <phrase role="special">=</phrase> <phrase role="identifier">boost</phrase><phrase role="special">::</phrase><phrase role="identifier">is_convertible</phrase><phrase role="special"><</phrase><phrase role="identifier">D</phrase><phrase role="special">*,</phrase><phrase role="identifier">A</phrase><phrase role="special">*>::</phrase><phrase role="identifier">value</phrase><phrase role="special">;</phrase> +</programlisting> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 4 and 8.5. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> This template is + currently broken with Borland C++ Builder 5 (and earlier), for constructor-based + conversions, and for the Metrowerks 7 (and earlier) compiler in all cases. + If the compiler does not support <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.is_abstract">is_abstract</link></computeroutput>, + then the template parameter <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">To</phrase></computeroutput> + must not be an abstract type. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_convertible</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_convertible</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">,</phrase> <phrase role="keyword">double</phrase><phrase role="special">></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_convertible</phrase><phrase role="special"><</phrase><phrase role="keyword">const</phrase> <phrase role="keyword">int</phrase><phrase role="special">,</phrase> <phrase role="keyword">double</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_convertible</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">*</phrase> <phrase role="keyword">const</phrase><phrase role="special">,</phrase> <phrase role="keyword">int</phrase><phrase role="special">*>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_convertible</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">*,</phrase> <phrase role="keyword">int</phrase><phrase role="special">*>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>false</emphasis>: + the conversion would require a <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">const_cast</phrase></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_convertible</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">&,</phrase> <phrase role="keyword">long</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_convertible</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_convertible</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_empty"><indexterm type="class_name"><primary>is_empty</primary><secondary>is_empty</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_empty"> is_empty</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_empty</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is an empty class type then + inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 10p5. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_empty</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> In order to correctly + detect empty classes this trait relies on either: + </para> + <itemizedlist> + <listitem> + the compiler implementing zero sized empty base classes, or + </listitem> + <listitem> + the compiler providing <link linkend="boost_typetraits.intrinsics">intrinsics</link> + to detect empty classes. + </listitem> + </itemizedlist> + <para> + Can not be used with incomplete types. + </para> + <para> + Can not be used with union types, until is_union can be made to work. + </para> + <para> + If the compiler does not support partial-specialization of class templates, + then this template can not be used with abstract types. + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + Given: <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">struct</phrase> <phrase role="identifier">empty_class</phrase> + <phrase role="special">{};</phrase></computeroutput> + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_empty</phrase><phrase role="special"><</phrase><phrase role="identifier">empty_class</phrase><phrase role="special">></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_empty</phrase><phrase role="special"><</phrase><phrase role="identifier">empty_class</phrase> <phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_empty</phrase><phrase role="special"><</phrase><phrase role="identifier">empty_class</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_empty</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_enum"><indexterm type="class_name"><primary>is_enum</primary><secondary>is_enum</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_enum"> is_enum</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_enum</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + enum type then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.2 and 7.2. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_enum</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> Requires a correctly + functioning <link linkend="boost_typetraits.reference.is_convertible">is_convertible</link> + template; this means that is_enum is currently broken under Borland C++ Builder + 5, and for the Metrowerks compiler prior to version 8, other compilers should + handle this template just fine. + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + Given: <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">enum</phrase> <phrase role="identifier">my_enum</phrase> + <phrase role="special">{</phrase> <phrase role="identifier">one</phrase><phrase role="special">,</phrase> <phrase role="identifier">two</phrase> <phrase role="special">};</phrase></computeroutput> + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_enum</phrase><phrase role="special"><</phrase><phrase role="identifier">my_enum</phrase><phrase role="special">></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_enum</phrase><phrase role="special"><</phrase><phrase role="identifier">my_enum</phrase> <phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_enum</phrase><phrase role="special"><</phrase><phrase role="identifier">my_enum</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_enum</phrase><phrase role="special"><</phrase><phrase role="identifier">my_enum</phrase><phrase role="special">&>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_enum</phrase><phrase role="special"><</phrase><phrase role="identifier">my_enum</phrase><phrase role="special">*>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_enum</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_floating_point"><indexterm type="class_name"><primary>is_floating_point</primary><secondary>is_floating_point</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_floating_point"> is_floating_point</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_floating_point</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + floating point type then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.1p8. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_floating_point</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_floating_point</phrase><phrase role="special"><</phrase><phrase role="keyword">float</phrase><phrase role="special">></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_floating_point</phrase><phrase role="special"><</phrase><phrase role="keyword">double</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_floating_point</phrase><phrase role="special"><</phrase><phrase role="keyword">long</phrase> <phrase role="keyword">double</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_floating_point</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_function"><indexterm type="class_name"><primary>is_function</primary><secondary>is_function</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_function"> is_function</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_function</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + function type then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + Note that this template does not detect <emphasis>pointers to functions</emphasis>, + or <emphasis>references to functions</emphasis>, these are detected by <link linkend="boost_typetraits.reference.is_pointer">is_pointer</link> and <link linkend="boost_typetraits.reference.is_reference">is_reference</link> respectively: + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">typedef</phrase> <phrase role="keyword">int</phrase> <phrase role="identifier">f1</phrase><phrase role="special">();</phrase> <phrase role="comment">// f1 is of function type. +</phrase><phrase role="keyword">typedef</phrase> <phrase role="keyword">int</phrase> <phrase role="special">(</phrase><phrase role="identifier">f2</phrase><phrase role="special">*)();</phrase> <phrase role="comment">// f2 is a pointer to a function. +</phrase><phrase role="keyword">typedef</phrase> <phrase role="keyword">int</phrase> <phrase role="special">(</phrase><phrase role="identifier">f3</phrase><phrase role="special">&)();</phrase> <phrase role="comment">// f3 is a reference to a function. +</phrase></programlisting> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.2p1 and 8.3.5. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_function</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_function</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(</phrase><phrase role="keyword">void</phrase><phrase role="special">)></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_function</phrase><phrase role="special"><</phrase><phrase role="keyword">long</phrase> <phrase role="special">(</phrase><phrase role="keyword">double</phrase><phrase role="special">,</phrase> <phrase role="keyword">int</phrase><phrase role="special">)>::</phrase><phrase role="identifier">type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_function</phrase><phrase role="special"><</phrase><phrase role="keyword">long</phrase> <phrase role="special">(</phrase><phrase role="keyword">double</phrase><phrase role="special">,</phrase> <phrase role="keyword">int</phrase><phrase role="special">)>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_function</phrase><phrase role="special"><</phrase><phrase role="keyword">long</phrase> <phrase role="special">(*)(</phrase><phrase role="keyword">double</phrase><phrase role="special">,</phrase> <phrase role="keyword">int</phrase><phrase role="special">)>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>: the argument in this case + is a pointer type, not a function type. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_function</phrase><phrase role="special"><</phrase><phrase role="keyword">long</phrase> <phrase role="special">(&)(</phrase><phrase role="keyword">double</phrase><phrase role="special">,</phrase> <phrase role="keyword">int</phrase><phrase role="special">)>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>: the argument in this case + is a reference to a function, not a function type. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_function</phrase><phrase role="special"><</phrase><phrase role="keyword">long</phrase> <phrase role="special">(</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">::*)(</phrase><phrase role="keyword">double</phrase><phrase role="special">,</phrase> <phrase role="keyword">int</phrase><phrase role="special">)>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>: the argument in this case + is a pointer to a member function. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_function</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + <tip> + <para> + Don't confuse function-types with pointers to functions: + </para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">typedef</phrase> <phrase role="keyword">int</phrase> + <phrase role="identifier">f</phrase><phrase role="special">(</phrase><phrase role="keyword">double</phrase><phrase role="special">);</phrase></computeroutput> + </para> + <para> + defines a function type, + </para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">f</phrase> <phrase role="identifier">foo</phrase><phrase role="special">;</phrase></computeroutput> + </para> + <para> + declares a prototype for a function of type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">f</phrase></computeroutput>, + </para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">f</phrase><phrase role="special">*</phrase> + <phrase role="identifier">pf</phrase> <phrase role="special">=</phrase> + <phrase role="identifier">foo</phrase><phrase role="special">;</phrase></computeroutput> + </para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">f</phrase><phrase role="special">&</phrase> + <phrase role="identifier">fr</phrase> <phrase role="special">=</phrase> + <phrase role="identifier">foo</phrase><phrase role="special">;</phrase></computeroutput> + </para> + <para> + declares a pointer and a reference to the function <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">foo</phrase></computeroutput>. + </para> + <para> + If you want to detect whether some type is a pointer-to-function then use: + </para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.is_function">is_function</link><phrase role="special"><</phrase><link linkend="boost_typetraits.reference.remove_pointer">remove_pointer</link><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase> + <phrase role="special">&&</phrase> <link linkend="boost_typetraits.reference.is_pointer">is_pointer</link><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> + </para> + <para> + or for pointers to member functions you can just use <link linkend="boost_typetraits.reference.is_member_function_pointer">is_member_function_pointer</link> + directly. + </para> + </tip> + </section> + <section id="boost_typetraits.reference.is_fundamental"><indexterm type="class_name"><primary>is_fundamental</primary><secondary>is_fundamental</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_fundamental"> is_fundamental</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_fundamental</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + fundamental type then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + Fundamental types include integral, floating point and void types (see also + <link linkend="boost_typetraits.reference.is_integral">is_integral</link>, + <link linkend="boost_typetraits.reference.is_floating_point">is_floating_point</link> + and <link linkend="boost_typetraits.reference.is_void">is_void</link>) + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.1. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_fundamental</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_fundamental</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">)></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_fundamental</phrase><phrase role="special"><</phrase><phrase role="keyword">double</phrase> <phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_fundamental</phrase><phrase role="special"><</phrase><phrase role="keyword">void</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_fundamental</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_integral"><indexterm type="class_name"><primary>is_integral</primary><secondary>is_integral</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_integral"> is_integral</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_integral</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + integral type then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.1p7. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_integral</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_integral</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_integral</phrase><phrase role="special"><</phrase><phrase role="keyword">const</phrase> <phrase role="keyword">char</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_integral</phrase><phrase role="special"><</phrase><phrase role="keyword">long</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_integral</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_member_function_pointer"><indexterm type="class_name"><primary>is_member_function_pointer</primary><secondary>is_member_function_pointer</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_member_function_pointer"> + is_member_function_pointer</link></title> +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_member_function_pointer</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + pointer to a member function then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.2 and 8.3.3. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_member_function_pointer</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_member_function_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">::*)(</phrase><phrase role="keyword">void</phrase><phrase role="special">)></phrase></computeroutput> inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_member_function_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">::*)(</phrase><phrase role="keyword">char</phrase><phrase role="special">)>::</phrase><phrase role="identifier">type</phrase></computeroutput> + is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_member_function_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">::*)(</phrase><phrase role="keyword">void</phrase><phrase role="special">)</phrase><phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_member_function_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">::*)>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>false</emphasis>: + the argument in this case is a pointer to a data member and not a member + function, see <link linkend="boost_typetraits.reference.is_member_object_pointer">is_member_object_pointer</link> + and <link linkend="boost_typetraits.reference.is_member_pointer">is_member_pointer</link> + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_member_function_pointer</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> + is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_member_object_pointer"><indexterm type="class_name"><primary>is_member_object_pointer</primary><secondary>is_member_object_pointer</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_member_object_pointer"> + is_member_object_pointer</link></title> +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_member_object_pointer</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + pointer to a member object (a data member) then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.2 and 8.3.3. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_member_object_pointer</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_member_object_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">::*)></phrase></computeroutput> inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_member_object_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">double</phrase> <phrase role="special">(</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">::*)>::</phrase><phrase role="identifier">type</phrase></computeroutput> + is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_member_object_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">const</phrase> <phrase role="keyword">int</phrase> <phrase role="special">(</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">::*)>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_member_object_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">::*)(</phrase><phrase role="keyword">void</phrase><phrase role="special">)>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>false</emphasis>: + the argument in this case is a pointer to a member function and not a + member object, see <link linkend="boost_typetraits.reference.is_member_function_pointer">is_member_function_pointer</link> + and <link linkend="boost_typetraits.reference.is_member_pointer">is_member_pointer</link> + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_member_object_pointer</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> + is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_member_pointer"><indexterm type="class_name"><primary>is_member_pointer</primary><secondary>is_member_pointer</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_member_pointer"> is_member_pointer</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_member_pointer</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + pointer to a member (either a function or a data member) then inherits from + <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.2 and 8.3.3. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_member_pointer</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_member_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">::*)></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_member_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">::*)(</phrase><phrase role="keyword">char</phrase><phrase role="special">)>::</phrase><phrase role="identifier">type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_member_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">::*)(</phrase><phrase role="keyword">void</phrase><phrase role="special">)</phrase><phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_member_pointer</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_object"><indexterm type="class_name"><primary>is_object</primary><secondary>is_object</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_object"> is_object</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_object</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + object type then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + All types are object types except references, void, and function types. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9p9. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_object</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_object</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_object</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">*>::</phrase><phrase role="identifier">type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_object</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(*)(</phrase><phrase role="keyword">void</phrase><phrase role="special">)>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_object</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">::*)(</phrase><phrase role="keyword">void</phrase><phrase role="special">)</phrase><phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_object</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">&>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>: reference types are not + objects + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_object</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(</phrase><phrase role="keyword">double</phrase><phrase role="special">)>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>: function types are not + objects + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_object</phrase><phrase role="special"><</phrase><phrase role="keyword">const</phrase> <phrase role="keyword">void</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>false</emphasis>: + void is not an object type + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_object</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_pod"> + <title><link linkend="boost_typetraits.reference.is_pod"> is_pod</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_pod</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + POD type then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + POD stands for "Plain old data". Arithmetic types, and enumeration + types, a pointers and pointer to members are all PODs. Classes and unions + can also be POD's if they have no non-static data members that are of reference + or non-POD type, no user defined constructors, no user defined assignment + operators, no private or protected non-static data members, no virtual functions + and no base classes. Finally, a cv-qualified POD is still a POD, as is an + array of PODs. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9p10 and 9p4 (Note + that POD's are also aggregates, see 8.5.1). + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial-specialization of class templates, then this template + can not be used with function types. + </para> + <para> + Without some (as yet unspecified) help from the compiler, is<emphasis role="underline">pod + will never report that a class or struct is a POD; this is always safe, if + possibly sub-optimal. Currently (May 2005) only MWCW 9 and Visual C++ 8 have + the necessary compiler-</emphasis>_intrinsics. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_pod</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_pod</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_pod</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase><phrase role="special">*>::</phrase><phrase role="identifier">type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_pod</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(*)(</phrase><phrase role="keyword">long</phrase><phrase role="special">)>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_pod</phrase><phrase role="special"><</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_pod</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_pointer"><indexterm type="class_name"><primary>is_pointer</primary><secondary>is_pointer</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_pointer"> is_pointer</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_pointer</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + pointer type (includes function pointers, but excludes pointers to members) + then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.2p2 and 8.3.1. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_pointer</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">*></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase><phrase role="special">*</phrase> <phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(*)(</phrase><phrase role="keyword">long</phrase><phrase role="special">)>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">::*)(</phrase><phrase role="keyword">long</phrase><phrase role="special">)>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">::*)>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_pointer</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + <important> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_pointer</phrase></computeroutput> detects "real" + pointer types only, and <emphasis>not</emphasis> smart pointers. Users + should not specialise <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_pointer</phrase></computeroutput> + for smart pointer types, as doing so may cause Boost (and other third party) + code to fail to function correctly. Users wanting a trait to detect smart + pointers should create their own. However, note that there is no way in + general to auto-magically detect smart pointer types, so such a trait would + have to be partially specialised for each supported smart pointer type. + </para> + </important> + </section> + <section id="boost_typetraits.reference.is_polymorphic"><indexterm type="class_name"><primary>is_polymorphic</primary><secondary>is_polymorphic</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_polymorphic"> is_polymorphic</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_polymorphic</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + polymorphic type then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + Type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> must be a complete + type. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 10.3. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> The implementation + requires some knowledge of the compilers ABI, it does actually seem to work + with the majority of compilers though. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_polymorphic</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + Given: <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">class</phrase> <phrase role="identifier">poly</phrase><phrase role="special">{</phrase> <phrase role="keyword">virtual</phrase> <phrase role="special">~</phrase><phrase role="identifier">poly</phrase><phrase role="special">();</phrase> <phrase role="special">};</phrase></computeroutput> + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_polymorphic</phrase><phrase role="special"><</phrase><phrase role="identifier">poly</phrase><phrase role="special">></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_polymorphic</phrase><phrase role="special"><</phrase><phrase role="identifier">poly</phrase> <phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_polymorphic</phrase><phrase role="special"><</phrase><phrase role="identifier">poly</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_polymorphic</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_same"><indexterm type="class_name"><primary>is_same</primary><secondary>is_same</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_same"> is_same</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">,</phrase> <phrase role="keyword">class</phrase> <phrase role="identifier">U</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_same</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T and U are the same types + then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_same</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial-specialization of class templates, then this template + can not be used with abstract, incomplete or function types. + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_same</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">,</phrase> <phrase role="keyword">int</phrase><phrase role="special">></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_same</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">,</phrase> <phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_same</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">,</phrase> <phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_same</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">,</phrase> <phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_same</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">&,</phrase> <phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_same</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_scalar"><indexterm type="class_name"><primary>is_scalar</primary><secondary>is_scalar</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_scalar"> is_scalar</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_scalar</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + scalar type then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + Scalar types include integral, floating point, enumeration, pointer, and + pointer-to-member types. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9p10. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_scalar</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial-specialization of class templates, then this template + can not be used with function types. + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_scalar</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">*></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_scalar</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_scalar</phrase><phrase role="special"><</phrase><phrase role="keyword">double</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_scalar</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(*)(</phrase><phrase role="keyword">long</phrase><phrase role="special">)>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_scalar</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">::*)(</phrase><phrase role="keyword">long</phrase><phrase role="special">)>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_scalar</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(</phrase><phrase role="identifier">MyClass</phrase><phrase role="special">::*)>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_scalar</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_signed"><indexterm type="class_name"><primary>is_signed</primary><secondary>is_signed</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_signed"> is_signed</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_signed</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is an signed integer type + or an enumerated type with an underlying signed integer type, then inherits + from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.1, 7.2. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_signed</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_signed</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_signed</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase> <phrase role="keyword">volatile</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_signed</phrase><phrase role="special"><</phrase><phrase role="keyword">unsigned</phrase> <phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_signed</phrase><phrase role="special"><</phrase><phrase role="identifier">myclass</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_signed</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + whose value depends upon the signedness of type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">char</phrase></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_signed</phrase><phrase role="special"><</phrase><phrase role="keyword">long</phrase> <phrase role="keyword">long</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_signed</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_stateless"> + <title><link linkend="boost_typetraits.reference.is_stateless"> is_stateless</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_stateless</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> Ff T is a stateless type then + inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + Type T must be a complete type. + </para> + <para> + A stateless type is a type that has no storage and whose constructors and + destructors are trivial. That means that <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_stateless</phrase></computeroutput> + only inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link> + if the following expression is <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">true</phrase></computeroutput>: + </para> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="special">::</phrase><phrase role="identifier">boost</phrase><phrase role="special">::</phrase><phrase role="identifier">has_trivial_constructor</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase> +<phrase role="special">&&</phrase> <phrase role="special">::</phrase><phrase role="identifier">boost</phrase><phrase role="special">::</phrase><phrase role="identifier">has_trivial_copy</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase> +<phrase role="special">&&</phrase> <phrase role="special">::</phrase><phrase role="identifier">boost</phrase><phrase role="special">::</phrase><phrase role="identifier">has_trivial_destructor</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase> +<phrase role="special">&&</phrase> <phrase role="special">::</phrase><phrase role="identifier">boost</phrase><phrase role="special">::</phrase><phrase role="identifier">is_class</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase> +<phrase role="special">&&</phrase> <phrase role="special">::</phrase><phrase role="identifier">boost</phrase><phrase role="special">::</phrase><phrase role="identifier">is_empty</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase> +</programlisting> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9p10. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_stateless</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial-specialization of class templates, then this template + can not be used with function types. + </para> + <para> + Without some (as yet unspecified) help from the compiler, is_stateless will + never report that a class or struct is stateless; this is always safe, if + possibly sub-optimal. Currently (May 2005) only MWCW 9 and Visual C++ 8 have + the necessary compiler <link linkend="boost_typetraits.intrinsics">intrinsics</link> + to make this template work automatically. + </para> + </section> + <section id="boost_typetraits.reference.is_reference"><indexterm type="class_name"><primary>is_reference</primary><secondary>is_reference</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_reference"> is_reference</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_reference</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a reference pointer type + then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.2 and 8.3.2. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial-specialization of class templates, then this template + may report the wrong result for function types, and for types that are both + const and volatile qualified. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_reference</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_reference</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">&></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_reference</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">&>::</phrase><phrase role="identifier">type</phrase></computeroutput> + is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_reference</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="special">(&)(</phrase><phrase role="keyword">long</phrase><phrase role="special">)>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis> (the argument in this case + is a reference to a function). + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_reference</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_union"><indexterm type="class_name"><primary>is_union</primary><secondary>is_union</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_union"> is_union</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_union</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + union type then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + Currently requires some kind of compiler support, otherwise unions are identified + as classes. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.2 and 9.5. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> Without (some as + yet unspecified) help from the compiler, we cannot distinguish between union + and class types using only standard C++, as a result this type will never + inherit from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + unless the user explicitly specializes the template for their user-defined + union types, or unless the compiler supplies some unspecified intrinsic that + implements this functionality. Currently (May 2005) only Visual C++ 8 has + the necessary compiler <link linkend="boost_typetraits.intrinsics">intrinsics</link> + to make this trait "just work" without user intervention. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_union</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_union</phrase><phrase role="special"><</phrase><phrase role="keyword">void</phrase><phrase role="special">></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_union</phrase><phrase role="special"><</phrase><phrase role="keyword">const</phrase> <phrase role="keyword">void</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_union</phrase><phrase role="special"><</phrase><phrase role="keyword">void</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_union</phrase><phrase role="special"><</phrase><phrase role="keyword">void</phrase><phrase role="special">*>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_union</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_unsigned"><indexterm type="class_name"><primary>is_unsigned</primary><secondary>is_unsigned</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_unsigned"> is_unsigned</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_unsigned</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is an unsigned integer type + or an enumerated type with an underlying unsigned integer type, then inherits + from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.1, 7.2. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_unsigned</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_unsigned</phrase><phrase role="special"><</phrase><phrase role="keyword">unsigned</phrase> <phrase role="keyword">int</phrase><phrase role="special">></phrase></computeroutput> inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_unsigned</phrase><phrase role="special"><</phrase><phrase role="keyword">unsigned</phrase> <phrase role="keyword">int</phrase> + <phrase role="keyword">const</phrase> <phrase role="keyword">volatile</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_unsigned</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_unsigned</phrase><phrase role="special"><</phrase><phrase role="identifier">myclass</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_unsigned</phrase><phrase role="special"><</phrase><phrase role="keyword">char</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + whose value depends upon the signedness of type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">char</phrase></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_unsigned</phrase><phrase role="special"><</phrase><phrase role="keyword">unsigned</phrase> <phrase role="keyword">long</phrase> + <phrase role="keyword">long</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_unsigned</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_void"><indexterm type="class_name"><primary>is_void</primary><secondary>is_void</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_void"> is_void</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_void</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (possibly cv-qualified) + void type then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.1p9. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_void</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_void</phrase><phrase role="special"><</phrase><phrase role="keyword">void</phrase><phrase role="special">></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_void</phrase><phrase role="special"><</phrase><phrase role="keyword">const</phrase> <phrase role="keyword">void</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_void</phrase><phrase role="special"><</phrase><phrase role="keyword">void</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_void</phrase><phrase role="special"><</phrase><phrase role="keyword">void</phrase><phrase role="special">*>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>false</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_void</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.is_volatile"><indexterm type="class_name"><primary>is_volatile</primary><secondary>is_volatile</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.is_volatile"> is_volatile</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">is_volatile</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <replaceable><link linkend="boost_typetraits.reference.integral_constant">true_type</link>-or-<link linkend="boost_typetraits.reference.integral_constant">false_type</link></replaceable> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> If T is a (top level) volatile-qualified + type then inherits from <link linkend="boost_typetraits.reference.integral_constant">true_type</link>, + otherwise inherits from <link linkend="boost_typetraits.reference.integral_constant">false_type</link>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.3. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">is_volatile</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_volatile</phrase><phrase role="special"><</phrase><phrase role="keyword">volatile</phrase> <phrase role="keyword">int</phrase><phrase role="special">></phrase></computeroutput> inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_volatile</phrase><phrase role="special"><</phrase><phrase role="keyword">const</phrase> <phrase role="keyword">volatile</phrase> + <phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">true_type</link></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_volatile</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">*</phrase> <phrase role="keyword">volatile</phrase><phrase role="special">>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>true</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_volatile</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">volatile</phrase><phrase role="special">*>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>false</emphasis>: + the volatile qualifier is not at the top level in this case. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">is_volatile</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">bool</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.make_signed"><indexterm type="class_name"><primary>make_signed</primary><secondary>make_signed</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.make_signed"> make_signed</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">make_signed</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + <emphasis role="bold">type:</emphasis> If T is a signed integer type then + the same type as T, if T is an unsigned integer type then the corresponding + signed type. Otherwise if T is an enumerated or character type (char or wchar_t) + then a signed integer type with the same width as T. + </para> + <para> + If T has any cv-qualifiers then these are also present on the result type. + </para> + <para> + <emphasis role="bold">Requires:</emphasis> T must be an integer or enumerated + type, and must not be the type bool. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.1. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">make_signed</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <table frame="all"> <title>Examples</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Expression + </para> + </entry><entry> + <para> + Result Type + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">make_signed</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">make_signed</phrase><phrase role="special"><</phrase><phrase role="keyword">unsigned</phrase> <phrase role="keyword">int</phrase> + <phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">make_signed</phrase><phrase role="special"><</phrase><phrase role="keyword">const</phrase> <phrase role="keyword">unsigned</phrase> + <phrase role="keyword">long</phrase> <phrase role="keyword">long</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">const</phrase> <phrase role="keyword">long</phrase> + <phrase role="keyword">long</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">make_signed</phrase><phrase role="special"><</phrase><phrase role="identifier">my_enum</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + A signed integer type with the same width as the enum. + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">make_signed</phrase><phrase role="special"><</phrase><phrase role="keyword">wchar_t</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + A signed integer type with the same width as wchar_t. + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section id="boost_typetraits.reference.make_unsigned"><indexterm type="class_name"><primary>make_unsigned</primary><secondary>make_unsigned</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.make_unsigned"> make_unsigned</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">make_unsigned</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + <emphasis role="bold">type:</emphasis> If T is a unsigned integer type then + the same type as T, if T is an signed integer type then the corresponding + unsigned type. Otherwise if T is an enumerated or character type (char or + wchar_t) then an unsigned integer type with the same width as T. + </para> + <para> + If T has any cv-qualifiers then these are also present on the result type. + </para> + <para> + <emphasis role="bold">Requires:</emphasis> T must be an integer or enumerated + type, and must not be the type bool. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.1. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">make_unsigned</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <table frame="all"> <title>Examples</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Expression + </para> + </entry><entry> + <para> + Result Type + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">make_signed</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">unsigned</phrase> <phrase role="keyword">int</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">make_signed</phrase><phrase role="special"><</phrase><phrase role="keyword">unsigned</phrase> <phrase role="keyword">int</phrase> + <phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">unsigned</phrase> <phrase role="keyword">int</phrase> + <phrase role="keyword">const</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">make_signed</phrase><phrase role="special"><</phrase><phrase role="keyword">const</phrase> <phrase role="keyword">unsigned</phrase> + <phrase role="keyword">long</phrase> <phrase role="keyword">long</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">const</phrase> <phrase role="keyword">unsigned</phrase> + <phrase role="keyword">long</phrase> <phrase role="keyword">long</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">make_signed</phrase><phrase role="special"><</phrase><phrase role="identifier">my_enum</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + An unsigned integer type with the same width as the enum. + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">make_signed</phrase><phrase role="special"><</phrase><phrase role="keyword">wchar_t</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + An unsigned integer type with the same width as wchar_t. + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section id="boost_typetraits.reference.promote"><indexterm type="class_name"><primary>promote</primary><secondary>promote</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.promote"> promote</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">promote</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + <emphasis role="bold">type:</emphasis> If integral or floating point promotion + can be applied to an rvalue of type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput>, + then applies integral and floating point promotions to <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> + and keeps cv-qualifiers of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput>, + otherwise leaves <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> unchanged. + See also <link linkend="boost_typetraits.reference.integral_promotion">integral_promotion</link> + and <link linkend="boost_typetraits.reference.floating_point_promotion">floating_point_promotion</link>. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 4.5 except 4.5/3 + (integral bit-field) and 4.6. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">promote</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <table frame="all"> <title>Examples</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Expression + </para> + </entry><entry> + <para> + Result Type + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">promote</phrase><phrase role="special"><</phrase><phrase role="keyword">short</phrase> <phrase role="keyword">volatile</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">volatile</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">promote</phrase><phrase role="special"><</phrase><phrase role="keyword">float</phrase> <phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">double</phrase> <phrase role="keyword">const</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">promote</phrase><phrase role="special"><</phrase><phrase role="keyword">short</phrase><phrase role="special">&>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">short</phrase><phrase role="special">&</phrase></computeroutput> + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section id="boost_typetraits.reference.rank"><indexterm type="class_name"><primary>integral_constant</primary><secondary>rank</secondary></indexterm><indexterm><primary>rank</primary><secondary>integral_constant</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.rank"> rank</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">rank</phrase> <phrase role="special">:</phrase> <phrase role="keyword">public</phrase> <link linkend="boost_typetraits.reference.integral_constant">integral_constant</link><phrase role="special"><</phrase><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase><phrase role="special">,</phrase> <phrase role="identifier">RANK</phrase><phrase role="special">(</phrase><phrase role="identifier">T</phrase><phrase role="special">)></phrase> <phrase role="special">{};</phrase> +</programlisting> + <para> + <emphasis role="bold">Inherits:</emphasis> Class template rank inherits from + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">integral_constant</link><phrase role="special"><</phrase><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase><phrase role="special">,</phrase> <phrase role="identifier">RANK</phrase><phrase role="special">(</phrase><phrase role="identifier">T</phrase><phrase role="special">)></phrase></computeroutput>, + where <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">RANK</phrase><phrase role="special">(</phrase><phrase role="identifier">T</phrase><phrase role="special">)</phrase></computeroutput> is the + number of array dimensions in type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput>. + </para> + <para> + If <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> is not an array type, + then <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">RANK</phrase><phrase role="special">(</phrase><phrase role="identifier">T</phrase><phrase role="special">)</phrase></computeroutput> is zero. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">rank</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <para> + <emphasis role="bold">Examples:</emphasis> + </para> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">rank</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">[]></phrase></computeroutput> + inherits from <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">integral_constant</link><phrase role="special"><</phrase><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase><phrase role="special">,</phrase> <phrase role="number">1</phrase><phrase role="special">></phrase></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">rank</phrase><phrase role="special"><</phrase><phrase role="keyword">double</phrase><phrase role="special">[</phrase><phrase role="number">2</phrase><phrase role="special">][</phrase><phrase role="number">3</phrase><phrase role="special">][</phrase><phrase role="number">4</phrase><phrase role="special">]>::</phrase><phrase role="identifier">type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><link linkend="boost_typetraits.reference.integral_constant">integral_constant</link><phrase role="special"><</phrase><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase><phrase role="special">,</phrase> <phrase role="number">3</phrase><phrase role="special">></phrase></computeroutput>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">rank</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">[</phrase><phrase role="number">1</phrase><phrase role="special">]>::</phrase><phrase role="identifier">value</phrase></computeroutput> + is an integral constant expression that evaluates to <emphasis>1</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">rank</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">[][</phrase><phrase role="number">2</phrase><phrase role="special">]>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>2</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">rank</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">*>::</phrase><phrase role="identifier">value</phrase></computeroutput> is an integral constant expression + that evaluates to <emphasis>0</emphasis>. + </para> + </para> + </blockquote> + <blockquote> + <para> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">rank</phrase><phrase role="special"><</phrase><phrase role="identifier">T</phrase><phrase role="special">>::</phrase><phrase role="identifier">value_type</phrase></computeroutput> is the type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase></computeroutput>. + </para> + </para> + </blockquote> + </section> + <section id="boost_typetraits.reference.remove_all_extents"><indexterm type="class_name"><primary>remove_all_extents</primary><secondary>remove_all_extents</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.remove_all_extents"> remove_all_extents</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">remove_all_extents</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + <emphasis role="bold">type:</emphasis> If <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> + is an array type, then removes all of the array bounds on <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput>, + otherwise leaves <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> unchanged. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 8.3.4. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial specialization of class-templates then this template + will compile, but the member <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">type</phrase></computeroutput> + will always be the same as type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> + except where <link linkend="boost_typetraits.category.transform.broken_compiler_workarounds_">compiler + workarounds</link> have been applied. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">remove_all_extents</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <table frame="all"> <title>Examples</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Expression + </para> + </entry><entry> + <para> + Result Type + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_all_extents</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_all_extents</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">[</phrase><phrase role="number">2</phrase><phrase role="special">]>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_all_extents</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">[][</phrase><phrase role="number">2</phrase><phrase role="special">]>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_all_extents</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">[</phrase><phrase role="number">2</phrase><phrase role="special">][</phrase><phrase role="number">3</phrase><phrase role="special">][</phrase><phrase role="number">4</phrase><phrase role="special">]>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_all_extents</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">*>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">*</phrase></computeroutput> + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section id="boost_typetraits.reference.remove_const"><indexterm type="class_name"><primary>remove_const</primary><secondary>remove_const</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.remove_const"> remove_const</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">remove_const</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + <emphasis role="bold">type:</emphasis> The same type as <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput>, + but with any <emphasis>top level</emphasis> const-qualifier removed. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.3. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial specialization of class-templates then this template + will compile, but the member <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">type</phrase></computeroutput> + will always be the same as type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> + except where <link linkend="boost_typetraits.category.transform.broken_compiler_workarounds_">compiler + workarounds</link> have been applied. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">remove_const</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <table frame="all"> <title>Examples</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Expression + </para> + </entry><entry> + <para> + Result Type + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_const</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_const</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_const</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase> + <phrase role="keyword">volatile</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">volatile</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_const</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">&>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">&</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_const</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">*>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">*</phrase></computeroutput> + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section id="boost_typetraits.reference.remove_cv"><indexterm type="class_name"><primary>remove_cv</primary><secondary>remove_cv</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.remove_cv"> remove_cv</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">remove_cv</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + <emphasis role="bold">type:</emphasis> The same type as <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput>, + but with any <emphasis>top level</emphasis> cv-qualifiers removed. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.3. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial specialization of class-templates then this template + will compile, but the member <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">type</phrase></computeroutput> + will always be the same as type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> + except where <link linkend="boost_typetraits.category.transform.broken_compiler_workarounds_">compiler + workarounds</link> have been applied. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">remove_cv</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <table frame="all"> <title>Examples</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Expression + </para> + </entry><entry> + <para> + Result Type + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_cv</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_cv</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_cv</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase> + <phrase role="keyword">volatile</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_cv</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">&>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">&</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_cv</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">*>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">*</phrase></computeroutput> + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section id="boost_typetraits.reference.remove_extent"><indexterm type="class_name"><primary>remove_extent</primary><secondary>remove_extent</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.remove_extent"> remove_extent</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">remove_extent</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + <emphasis role="bold">type:</emphasis> If <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> + is an array type, then removes the topmost array bound, otherwise leaves + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> unchanged. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 8.3.4. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial specialization of class-templates then this template + will compile, but the member <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">type</phrase></computeroutput> + will always be the same as type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> + except where <link linkend="boost_typetraits.category.transform.broken_compiler_workarounds_">compiler + workarounds</link> have been applied. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">remove_extent</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <table frame="all"> <title>Examples</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Expression + </para> + </entry><entry> + <para> + Result Type + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_extent</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_extent</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">[</phrase><phrase role="number">2</phrase><phrase role="special">]>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_extent</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">[</phrase><phrase role="number">2</phrase><phrase role="special">][</phrase><phrase role="number">4</phrase><phrase role="special">]>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">[</phrase><phrase role="number">4</phrase><phrase role="special">]</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_extent</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">[][</phrase><phrase role="number">2</phrase><phrase role="special">]>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">[</phrase><phrase role="number">2</phrase><phrase role="special">]</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_extent</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">*>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">*</phrase></computeroutput> + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section id="boost_typetraits.reference.remove_pointer"><indexterm type="class_name"><primary>remove_pointer</primary><secondary>remove_pointer</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.remove_pointer"> remove_pointer</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">remove_pointer</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + <emphasis role="bold">type:</emphasis> The same type as <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput>, + but with any pointer modifier removed. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 8.3.1. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial specialization of class-templates then this template + will compile, but the member <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">type</phrase></computeroutput> + will always be the same as type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> + except where <link linkend="boost_typetraits.category.transform.broken_compiler_workarounds_">compiler + workarounds</link> have been applied. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">remove_pointer</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <table frame="all"> <title>Examples</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Expression + </para> + </entry><entry> + <para> + Result Type + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">*>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">**>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">*</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">&>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">&</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_pointer</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">*&>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">*&</phrase></computeroutput> + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section id="boost_typetraits.reference.remove_reference"><indexterm type="class_name"><primary>remove_reference</primary><secondary>remove_reference</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.remove_reference"> remove_reference</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">remove_reference</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + <emphasis role="bold">type:</emphasis> The same type as <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput>, + but with any reference modifier removed. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 8.3.2. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial specialization of class-templates then this template + will compile, but the member <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">type</phrase></computeroutput> + will always be the same as type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> + except where <link linkend="boost_typetraits.category.transform.broken_compiler_workarounds_">compiler + workarounds</link> have been applied. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">remove_reference</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <table frame="all"> <title>Examples</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Expression + </para> + </entry><entry> + <para> + Result Type + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_reference</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_reference</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">&>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_reference</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">*>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">*</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_reference</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">*&>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase><phrase role="special">*</phrase></computeroutput> + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section id="boost_typetraits.reference.remove_volatile"><indexterm type="class_name"><primary>remove_volatile</primary><secondary>remove_volatile</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.remove_volatile"> remove_volatile</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">remove_volatile</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + <emphasis role="bold">type:</emphasis> The same type as <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput>, + but with any <emphasis>top level</emphasis> volatile-qualifier removed. + </para> + <para> + <emphasis role="bold">C++ Standard Reference:</emphasis> 3.9.3. + </para> + <para> + <emphasis role="bold">Compiler Compatibility:</emphasis> If the compiler + does not support partial specialization of class-templates then this template + will compile, but the member <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">type</phrase></computeroutput> + will always be the same as type <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">T</phrase></computeroutput> + except where <link linkend="boost_typetraits.category.transform.broken_compiler_workarounds_">compiler + workarounds</link> have been applied. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">remove_volatile</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + <table frame="all"> <title>Examples</title> + <tgroup cols="2"> + <thead> + <row> + <entry> + <para> + Expression + </para> + </entry><entry> + <para> + Result Type + </para> + </entry> + </row> + </thead> + <tbody> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_volatile</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_volatile</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">volatile</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_volatile</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase> + <phrase role="keyword">volatile</phrase><phrase role="special">>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_volatile</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">volatile</phrase><phrase role="special">&>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">&</phrase></computeroutput> + </para> + </entry> + </row> + <row> + <entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">remove_volatile</phrase><phrase role="special"><</phrase><phrase role="keyword">int</phrase> <phrase role="keyword">volatile</phrase><phrase role="special">*>::</phrase><phrase role="identifier">type</phrase></computeroutput> + </para> + </entry><entry> + <para> + <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">int</phrase> <phrase role="keyword">const</phrase><phrase role="special">*</phrase></computeroutput> + </para> + </entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section id="boost_typetraits.reference.type_with_alignment"><indexterm type="class_name"><primary>type_with_alignment</primary><secondary>type_with_alignment</secondary></indexterm> + <title><link linkend="boost_typetraits.reference.type_with_alignment"> type_with_alignment</link></title> + +<programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="identifier">std</phrase><phrase role="special">::</phrase><phrase role="identifier">size_t</phrase> <phrase role="identifier">Align</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">type_with_alignment</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <para> + <emphasis role="bold">type:</emphasis> a built-in or POD type with an alignment + that is a multiple of <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="identifier">Align</phrase></computeroutput>. + </para> + <para> + <emphasis role="bold">Header:</emphasis> <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> + <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">/</phrase><phrase role="identifier">type_with_alignment</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + or <computeroutput xmlns:xi="http://www.w3.org/2001/XInclude"> <phrase role="preprocessor">#include</phrase> <phrase role="special"><</phrase><phrase role="identifier">boost</phrase><phrase role="special">/</phrase><phrase role="identifier">type_traits</phrase><phrase role="special">.</phrase><phrase role="identifier">hpp</phrase><phrase role="special">></phrase></computeroutput> + </para> + </section> + </section> + <section id="boost_typetraits.credits"> + <title><link linkend="boost_typetraits.credits"> Credits</link></title> + <para> + This documentation was pulled together by John Maddock, using <ulink url="../../../../doc/html/quickbook.html">Boost.Quickbook</ulink> + and <ulink url="../../../../doc/html/boostbook.html">Boost.DocBook</ulink>. + </para> + <para> + The original version of this library was created by Steve Cleary, Beman Dawes, + Howard Hinnant, and John Maddock. John Maddock is the current maintainer of + the library. + </para> + <para> + This version of type traits library is based on contributions by Adobe Systems + Inc, David Abrahams, Steve Cleary, Beman Dawes, Aleksey Gurtovoy, Howard Hinnant, + Jesse Jones, Mat Marcus, Itay Maman, John Maddock, Thorsten Ottosen, Robert + Ramey and Jeremy Siek. + </para> + <para> + Mat Marcus and Jesse Jones invented, and <ulink url="http://opensource.adobe.com/project4/project.shtml">published + a paper describing</ulink>, the partial specialization workarounds used in + this library. + </para> + <para> + Aleksey Gurtovoy added MPL integration to the library. + </para> + <para> + The <link linkend="boost_typetraits.reference.is_convertible">is_convertible</link> + template is based on code originally devised by Andrei Alexandrescu, see "<ulink url="http://www.cuj.com/experts/1810/alexandr.htm?topic=experts">Generic<Programming>: + Mappings between Types and Values</ulink>". + </para> + <para> + The latest version of this library and documentation can be found at <ulink url="http://www.boost.org">www.boost.org</ulink>. Bugs, suggestions and discussion + should be directed to boost@lists.boost.org (see <ulink url="http://www.boost.org/more/mailing_lists.htm#main">www.boost.org/more/mailing_lists.htm#main</ulink> + for subscription details). + </para> + </section> + + <section id="boost_typetraits.ignored_section"> + <title>This section must not be indexed.</title> + <?BoostAutoIndex IgnoreSection?> + <programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword">template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">add_const</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + </section> + + <section id="boost_typetraits.ignored_block"><indexterm type="class_name"><primary>add_volatile</primary><secondary>This section contains one block that must not be indexed and one that should be.</secondary></indexterm><indexterm><primary>This section contains one block that must not be indexed and one that should be.</primary><secondary>add_volatile</secondary></indexterm> + <title>This section contains one block that must not be indexed and one that should be.</title> + <programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword"> + <?BoostAutoIndex IgnoreBlock?> + template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">add_const</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + <programlisting xmlns:xi="http://www.w3.org/2001/XInclude"><phrase role="keyword"> + template</phrase> <phrase role="special"><</phrase><phrase role="keyword">class</phrase> <phrase role="identifier">T</phrase><phrase role="special">></phrase> +<phrase role="keyword">struct</phrase> <phrase role="identifier">add_volatile</phrase> +<phrase role="special">{</phrase> + <phrase role="keyword">typedef</phrase> <replaceable>see-below</replaceable> <phrase role="identifier">type</phrase><phrase role="special">;</phrase> +<phrase role="special">};</phrase> +</programlisting> + </section> + + + <index type="class_name"> + <title>Class Index</title> + </index> + <index type="typedef_name"> + <title>Typedef Index</title> + </index> + <index type="macro_name"> + <title>Macro Index</title> + </index> + <index type="test_index_1"> + <title>Index Test 1</title> + </index> + <index type="test_index_2"> + <title>Index Test 2</title> + </index> + <index/> + +</chapter>
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