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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-15 19:44:05 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-15 19:44:05 +0000 |
| commit | d318611dd6f23fcfedd50e9b9e24620b102ba96a (patch) | |
| tree | 8b9eef82ca40fdd5a8deeabf07572074c236095d /doc/groff.html.node/Operators-in-Conditionals.html | |
| parent | Initial commit. (diff) | |
| download | groff-upstream.tar.xz groff-upstream.zip | |
Adding upstream version 1.23.0.upstream/1.23.0upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'doc/groff.html.node/Operators-in-Conditionals.html')
| -rw-r--r-- | doc/groff.html.node/Operators-in-Conditionals.html | 222 |
1 files changed, 222 insertions, 0 deletions
diff --git a/doc/groff.html.node/Operators-in-Conditionals.html b/doc/groff.html.node/Operators-in-Conditionals.html new file mode 100644 index 0000000..a04b761 --- /dev/null +++ b/doc/groff.html.node/Operators-in-Conditionals.html @@ -0,0 +1,222 @@ +<!DOCTYPE html> +<html> +<!-- Created by GNU Texinfo 7.0.3, https://www.gnu.org/software/texinfo/ --> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> +<!-- This manual documents GNU troff version 1.23.0. + +Copyright © 1994-2023 Free Software Foundation, Inc. + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with no +Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A +copy of the license is included in the section entitled "GNU Free +Documentation License". --> +<title>Operators in Conditionals (The GNU Troff Manual)</title> + +<meta name="description" content="Operators in Conditionals (The GNU Troff Manual)"> +<meta name="keywords" content="Operators in Conditionals (The GNU Troff Manual)"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<meta name="viewport" content="width=device-width,initial-scale=1"> + +<link href="index.html" rel="start" title="Top"> +<link href="Request-Index.html" rel="index" title="Request Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Conditionals-and-Loops.html" rel="up" title="Conditionals and Loops"> +<link href="if_002dthen.html" rel="next" title="if-then"> +<link href="Conditionals-and-Loops.html" rel="prev" title="Conditionals and Loops"> +<style type="text/css"> +<!-- +a.copiable-link {visibility: hidden; text-decoration: none; line-height: 0em} +div.example {margin-left: 3.2em} +span:hover a.copiable-link {visibility: visible} +--> +</style> + + +</head> + +<body lang="en"> +<div class="subsection-level-extent" id="Operators-in-Conditionals"> +<div class="nav-panel"> +<p> +Next: <a href="if_002dthen.html" accesskey="n" rel="next">if-then</a>, Previous: <a href="Conditionals-and-Loops.html" accesskey="p" rel="prev">Conditionals and Loops</a>, Up: <a href="Conditionals-and-Loops.html" accesskey="u" rel="up">Conditionals and Loops</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Request-Index.html" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<h4 class="subsection" id="Operators-in-Conditionals-1">5.23.1 Operators in Conditionals</h4> + +<a class="index-entry-id" id="index-if-request_002c-operators-to-use-with"></a> +<a class="index-entry-id" id="index-ie-request_002c-operators-to-use-with"></a> +<a class="index-entry-id" id="index-while-request_002c-operators-to-use-with"></a> +<a class="index-entry-id" id="index-conditional-expressions"></a> +<a class="index-entry-id" id="index-expressions_002c-conditional"></a> +<p>In <code class="code">if</code>, <code class="code">ie</code>, and <code class="code">while</code> requests, in addition to the +numeric expressions described in <a class="ref" href="Numeric-Expressions.html">Numeric Expressions</a>, several +Boolean operators are available; the members of this expanded class are +termed <em class="dfn">conditional expressions</em>. +</p> +<dl class="table"> +<dt><code class="code">c <var class="var">glyph</var></code></dt> +<dd><p>True if <var class="var">glyph</var> is available, where <var class="var">glyph</var> is an ordinary +character, a special character ‘<samp class="samp">\(<var class="var">xx</var></samp>’ or ‘<samp class="samp">\[<var class="var">xxx</var>]</samp>’, +‘<samp class="samp">\N'<var class="var">xxx</var>'</samp>’, or has been defined by any of the <code class="code">char</code>, +<code class="code">fchar</code>, <code class="code">fschar</code>, or <code class="code">schar</code> requests. +</p> +</dd> +<dt><code class="code">d <var class="var">name</var></code></dt> +<dd><p>True if a string, macro, diversion, or request called <var class="var">name</var> exists. +</p> +</dd> +<dt><code class="code">e</code></dt> +<dd><p>True if the current page is even-numbered. +</p> +</dd> +<dt><code class="code">F <var class="var">font</var></code></dt> +<dd><p>True if <var class="var">font</var> exists. <var class="var">font</var> is handled as if it were opened +with the <code class="code">ft</code> request (that is, font translation and styles are +applied), without actually mounting it. +</p> +</dd> +<dt><code class="code">m <var class="var">color</var></code></dt> +<dd><p>True if <var class="var">color</var> is defined. +</p> +</dd> +<dt id='index-conditional-output-for-terminal-_0028TTY_0029'><span><code class="code">n</code><a class="copiable-link" href='#index-conditional-output-for-terminal-_0028TTY_0029'> ¶</a></span></dt> +<dd><a class="index-entry-id" id="index-TTY_002c-conditional-output-for"></a> +<a class="index-entry-id" id="index-terminal_002c-conditional-output-for"></a> +<p>True if the document is being processed in <code class="code">nroff</code> mode. +See <a class="xref" href="troff-and-nroff-Modes.html"><code class="code">troff</code> and <code class="code">nroff</code> Modes</a>. +</p> +</dd> +<dt><code class="code">o</code></dt> +<dd><p>True if the current page is odd-numbered. +</p> +</dd> +<dt><code class="code">r <var class="var">register</var></code></dt> +<dd><p>True if <var class="var">register</var> exists. +</p> +</dd> +<dt><code class="code">S <var class="var">style</var></code></dt> +<dd><p>True if <var class="var">style</var> is available for the current font family. Font +translation is applied. +</p> +</dd> +<dt><code class="code">t</code></dt> +<dd><p>True if the document is being processed in <code class="code">troff</code> mode. +See <a class="xref" href="troff-and-nroff-Modes.html"><code class="code">troff</code> and <code class="code">nroff</code> Modes</a>. +</p> +<a class="index-entry-id" id="index-vtroff"></a> +</dd> +<dt><code class="code">v</code></dt> +<dd><p>Always false. This condition is recognized only for compatibility with +certain other <code class="code">troff</code> implementations.<a class="footnote" id="DOCF88" href="groff.html_fot.html#FOOT88"><sup>88</sup></a> +</p></dd> +</dl> + +<p>If the first argument to an <code class="code">if</code>, <code class="code">ie</code>, or <code class="code">while</code> +request begins with a non-alphanumeric character apart from <code class="code">!</code> +(see below); it performs an <i class="slanted">output comparison test</i>. +<a class="footnote" id="DOCF89" href="groff.html_fot.html#FOOT89"><sup>89</sup></a> +</p> +<a class="index-entry-id" id="index-output-comparison-operator"></a> +<dl class="table"> +<dt><code class="code"><code class="code">'</code><var class="var">xxx</var><code class="code">'</code><var class="var">yyy</var><code class="code">'</code></code></dt> +<dd><p>True if formatting the comparands <var class="var">xxx</var> and <var class="var">yyy</var> produces the +same output commands. The delimiter need not be a neutral apostrophe: +the output comparison operator accepts the same delimiters as most +escape sequences; see <a class="ref" href="Delimiters.html">Delimiters</a>. This <em class="dfn">output comparison +operator</em> formats <var class="var">xxx</var> and <var class="var">yyy</var> in separate environments; +after the comparison, the resulting data are discarded. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.ie "|"\fR|\fP" true +.el false + ⇒ true +</pre></div></div> + +<p>The resulting glyph properties, including font family, style, size, and +slant, must match, but not necessarily the requests and/or escape +sequences used to obtain them. In the previous example, ‘<samp class="samp">|</samp>’ and +‘<samp class="samp">\fR|\fP</samp>’ result in ‘<samp class="samp">|</samp>’ glyphs in the same typefaces at the +same positions, so the comparands are equal. If ‘<samp class="samp">.ft I</samp>’ had +been added before the ‘<samp class="samp">.ie</samp>’, they would differ: the first ‘<samp class="samp">|</samp>’ +would produce an italic ‘<samp class="samp">|</samp>’, not a roman one. Motions must match +in orientation and magnitude to within the applicable horizontal and +vertical motion quanta of the device, after rounding. ‘<samp class="samp">.if +"\u\d"\v'0'"</samp>’ is false even though both comparands result in zero net +motion, because motions are not interpreted or optimized but sent as-is +to the output.<a class="footnote" id="DOCF90" href="groff.html_fot.html#FOOT90"><sup>90</sup></a> On the other hand, ‘<samp class="samp">.if "\d"\v'0.5m'"</samp>’ is true, because +<code class="code">\d</code> is defined as a downward motion of one-half em.<a class="footnote" id="DOCF91" href="groff.html_fot.html#FOOT91"><sup>91</sup></a> +</p> +<a class="index-entry-id" id="index-string-comparison"></a> +<a class="index-entry-id" id="index-comparison-of-strings"></a> +<p>Surround the comparands with <code class="code">\?</code> to avoid formatting them; this +causes them to be compared character by character, as with string +comparisons in other programming languages. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.ie "\?|\?"\?\fR|\fP\?" true +.el false + ⇒ false +</pre></div></div> + +<a class="index-entry-id" id="index-_005c_003f_002c-and-copy-mode"></a> +<a class="index-entry-id" id="index-copy-mode_002c-and-_005c_003f"></a> +<a class="index-entry-id" id="index-mode_002c-copy_002c-and-_005c_003f"></a> +<p>Since comparands protected with <code class="code">\?</code> are read in copy mode +(see <a class="pxref" href="Copy-Mode.html">Copy Mode</a>), they need not even be valid <code class="code">groff</code> syntax. +The escape character is still lexically recognized, however, and +consumes the next character. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.ds a \[ +.ds b \[ +.if '\?\*a\?'\?\*b\?' a and b equivalent +.if '\?\\?'\?\\?' backslashes equivalent + ⇒ a and b equivalent +</pre></div></div> +</dd> +</dl> + +<p>The above operators can’t be combined with most others, but a leading +‘<samp class="samp">!</samp>’, not followed immediately by spaces or tabs, complements an +expression. +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.nr x 1 +.ie !r x register x is not defined +.el register x is defined + ⇒ register x is defined +</pre></div></div> + +<p>Spaces and tabs are optional immediately after the ‘<samp class="samp">c</samp>’, ‘<samp class="samp">d</samp>’, +‘<samp class="samp">F</samp>’, ‘<samp class="samp">m</samp>’, ‘<samp class="samp">r</samp>’, and ‘<samp class="samp">S</samp>’ operators, but right after +‘<samp class="samp">!</samp>’, they end the predicate and the conditional evaluates +true.<a class="footnote" id="DOCF92" href="groff.html_fot.html#FOOT92"><sup>92</sup></a> +</p> +<div class="example"> +<div class="group"><pre class="example-preformatted">.nr x 1 +.ie ! r x register x is not defined +.el register x is defined + ⇒ r x register x is not defined +</pre></div></div> + +<p>The unexpected ‘<samp class="samp">r x</samp>’ in the output is a clue that our conditional +was not interpreted as we planned, but matters may not always be so +obvious. +</p> + +</div> +<hr> +<div class="nav-panel"> +<p> +Next: <a href="if_002dthen.html">if-then</a>, Previous: <a href="Conditionals-and-Loops.html">Conditionals and Loops</a>, Up: <a href="Conditionals-and-Loops.html">Conditionals and Loops</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Request-Index.html" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html> |