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diff --git a/src/boost/libs/functional/function_traits.html b/src/boost/libs/functional/function_traits.html new file mode 100644 index 00000000..c0ce5108 --- /dev/null +++ b/src/boost/libs/functional/function_traits.html @@ -0,0 +1,233 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> + +<html> +<head> + <meta http-equiv="Content-Language" content="en-us"> + <meta http-equiv="Content-Type" content="text/html; charset=us-ascii"> + + <title>Boost Function Object Adapter Library</title> +</head> + +<body bgcolor="#FFFFFF" text="#000000"> + <table border="1" bgcolor="#007F7F" cellpadding="2" summary=""> + <tr> + <td bgcolor="#FFFFFF"><img src="../../boost.png" alt= + "boost.png (6897 bytes)" width="277" height="86"></td> + + <td><a href="../../index.htm"><font face="Arial" color= + "#FFFFFF"><big>Home</big></font></a></td> + + <td><a href="../libraries.htm"><font face="Arial" color= + "#FFFFFF"><big>Libraries</big></font></a></td> + + <td><a href="http://www.boost.org/people/people.htm"><font face="Arial" color= + "#FFFFFF"><big>People</big></font></a></td> + + <td><a href="http://www.boost.org/more/faq.htm"><font face="Arial" color= + "#FFFFFF"><big>FAQ</big></font></a></td> + + <td><a href="../../more/index.htm"><font face="Arial" color= + "#FFFFFF"><big>More</big></font></a></td> + </tr> + </table> + + <h1>Function Object Traits</h1> + + <p>The header <a href="../../boost/functional.hpp">functional.hpp</a> + provides two traits class templates for functions and function objects:</p> + + <table border="1" summary=""> + <tr> + <th>Type</th> + + <th>Contents</th> + + <th>Description</th> + </tr> + + <tr> + <td valign="top" rowspan="4"> + <tt>template <typename T><br> + struct unary_traits</tt></td> + + <td valign="top"><tt>function_type</tt></td> + + <td valign="top">The type of the function or function object itself + (i.e., <tt>T</tt>).</td> + </tr> + + <tr> + <td valign="top"><tt>param_type</tt></td> + + <td valign="top">The type that should be used to pass the function or + function object as a parameter.</td> + </tr> + + <tr> + <td valign="top"><tt>result_type</tt></td> + + <td valign="top">The type returned by the function or function + object.</td> + </tr> + + <tr> + <td valign="top"><tt>argument_type</tt></td> + + <td valign="top">The type of the argument to the function or function + object.</td> + </tr> + + <tr> + <td valign="top" rowspan="5"> + <tt>template <typename T><br> + struct binary_traits</tt></td> + + <td valign="top"><tt>function_type</tt></td> + + <td valign="top">The type of the function or function object itself + (i.e., <tt>T</tt>).</td> + </tr> + + <tr> + <td valign="top"><tt>param_type</tt></td> + + <td valign="top">The type that should be used to pass the function or + function object as a parameter.</td> + </tr> + + <tr> + <td valign="top"><tt>result_type</tt></td> + + <td valign="top">The type returned by the function or function + object.</td> + </tr> + + <tr> + <td valign="top"><tt>first_argument_type</tt></td> + + <td valign="top">The type of the first argument to the function or + function object.</td> + </tr> + + <tr> + <td valign="top"><tt>second_argument_type</tt></td> + + <td valign="top">The type of the second argument to the function or + function object.</td> + </tr> + </table> + + <h3>Usage</h3> + + <p><tt>unary_traits</tt> should be instantiated with either a function + taking a single parameter, or an adaptable unary function object (i.e., a + class derived from <tt>std::unary_function</tt> or one which provides the + same typedefs). (See §20.3.1 in the C++ Standard.)</p> + + <p><tt>binary_traits</tt> should be instantiated with either a function + taking two parameters, or an adaptable binary function object (i.e., a + class derived from <tt>std::binary_function</tt> or one which provides the + same typedefs). (See §20.3.1 in the C++ Standard.)</p> + + <p>The most common usage of these templates is in function object adapters, + thus allowing them to adapt plain functions as well as function objects. + You can do this by wherever you would normally write, for example,</p> + + <blockquote> + <pre> +typename Operation::argument_type +</pre> + </blockquote> + + <p>simply writing</p> + + <blockquote> + <pre> +typename boost::unary_traits<Operation>::argument_type +</pre> + </blockquote> + + <p>instead.</p> + + <h3>Additional Types Defined</h3> + + <p>In addition to the standard result and argument typedefs, these traits + templates define two additional types.</p> + + <h4><tt>function_type</tt></h4> + + <p>This is the type of the function or function object, and can be used in + declarations such as</p> + + <blockquote> + <pre> +template <class Predicate> +class unary_negate : // ... +{ + // ... + private: + <strong>typename unary_traits<Predicate>::function_type</strong> pred; +}; +</pre> + </blockquote> + + <p>If this typedef were not provided, it would not be possible to declare + <tt>pred</tt> in a way that would allow <tt>unary_negate</tt> to be + instantiated with a function type (see the C++ Standard §14.3.1 + ¶3).</p> + + <h4><tt>param_type</tt></h4> + + <p>This is a type suitable for passing the function or function object as a + parameter to another function. For example,</p> + + <blockquote> + <pre> +template <class Predicate> +class unary_negate : // ... +{ + public: + explicit unary_negate(<strong>typename unary_traits<Predicate>::param_type</strong> x) + : + pred(x) + {} + // ... +}; +</pre> + </blockquote> + + <p>Function objects are passed by reference to const; function pointers are + passed by value.</p> + + <h3>Limitations</h3> + + <p>This library uses these traits within all function object adapters, + theoretically rendering <tt>ptr_fun</tt> obsolete. However, third party + adapters probably won't take advantage of this mechanism, and so + <tt>ptr_fun</tt> may still be required. Accordingly, this library also + provides <a href="ptr_fun.html">improved versions of the standard function + pointer adapters</a>.</p> + + <p>These traits templates will also not work with compilers that fail to + support partial specialisation of templates. With these compilers, the + traits templates can only be instantiated with adaptable function objects, + thus requiring <tt>ptr_fun</tt> to be used, even with the function object + adapters in this library.</p> + <hr> + + <p><a href="http://validator.w3.org/check?uri=referer"><img border="0" src= + "../../doc/images/valid-html401.png" alt="Valid HTML 4.01 Transitional" + height="31" width="88"></a></p> + + <p>Revised + <!--webbot bot="Timestamp" s-type="EDITED" s-format="%d %B, %Y" startspan -->02 + December, 2006<!--webbot bot="Timestamp" endspan i-checksum="38510" --></p> + + <p><i>Copyright © 2000 Cadenza New Zealand Ltd.</i></p> + + <p><i>Distributed under the Boost Software License, Version 1.0. (See + accompanying file <a href="../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or + copy at <a href= + "http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</a>)</i></p> +</body> +</html> |