1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Directive Testing if Parser Succeeded (matches[])</title> 5<link rel="stylesheet" href="../../../../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../../../index.html" title="Spirit 2.5.8"> 8<link rel="up" href="../directive.html" title="Parser Directives"> 9<link rel="prev" href="repeat.html" title="Repetition Parser Directive (repeat[])"> 10<link rel="next" href="skip.html" title="Parser Directive Re-Establishing Skipping (skip[])"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../../../../index.html">Home</a></td> 16<td align="center"><a 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title="Directive Testing if Parser Succeeded (matches[])">Directive 28 Testing if Parser Succeeded (<code class="computeroutput"><span class="identifier">matches</span><span class="special">[]</span></code>)</a> 29</h5></div></div></div> 30<h6> 31<a name="spirit.qi.reference.directive.matches.h0"></a> 32 <span class="phrase"><a name="spirit.qi.reference.directive.matches.description"></a></span><a class="link" href="matches.html#spirit.qi.reference.directive.matches.description">Description</a> 33 </h6> 34<p> 35 The <code class="computeroutput"><span class="identifier">matches</span><span class="special">[]</span></code> 36 directive executes the embedded parser and returns whether it succeeded 37 matching. 38 </p> 39<h6> 40<a name="spirit.qi.reference.directive.matches.h1"></a> 41 <span class="phrase"><a name="spirit.qi.reference.directive.matches.header"></a></span><a class="link" href="matches.html#spirit.qi.reference.directive.matches.header">Header</a> 42 </h6> 43<pre class="programlisting"><span class="comment">// forwards to <boost/spirit/home/qi/directive/matches.hpp></span> 44<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">spirit</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">qi_matches</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 45</pre> 46<p> 47 Also, see <a class="link" href="../../../structure/include.html" title="Include">Include Structure</a>. 48 </p> 49<h6> 50<a name="spirit.qi.reference.directive.matches.h2"></a> 51 <span class="phrase"><a name="spirit.qi.reference.directive.matches.namespace"></a></span><a class="link" href="matches.html#spirit.qi.reference.directive.matches.namespace">Namespace</a> 52 </h6> 53<div class="informaltable"><table class="table"> 54<colgroup><col></colgroup> 55<thead><tr><th> 56 <p> 57 Name 58 </p> 59 </th></tr></thead> 60<tbody><tr><td> 61 <p> 62 <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">matches</span> <span class="comment">// 63 alias: boost::spirit::qi::matches</span></code> 64 </p> 65 </td></tr></tbody> 66</table></div> 67<h6> 68<a name="spirit.qi.reference.directive.matches.h3"></a> 69 <span class="phrase"><a name="spirit.qi.reference.directive.matches.model_of"></a></span><a class="link" href="matches.html#spirit.qi.reference.directive.matches.model_of">Model 70 of</a> 71 </h6> 72<div class="blockquote"><blockquote class="blockquote"><p> 73 <a class="link" href="../parser_concepts/unaryparser.html" title="UnaryParser"><code class="computeroutput"><span class="identifier">UnaryParser</span></code></a> 74 </p></blockquote></div> 75<div class="variablelist"> 76<p class="title"><b>Notation</b></p> 77<dl class="variablelist"> 78<dt><span class="term"><code class="computeroutput"><span class="identifier">a</span></code></span></dt> 79<dd><p> 80 A <a class="link" href="../parser_concepts/parser.html" title="Parser"><code class="computeroutput"><span class="identifier">Parser</span></code></a>. 81 </p></dd> 82</dl> 83</div> 84<h6> 85<a name="spirit.qi.reference.directive.matches.h4"></a> 86 <span class="phrase"><a name="spirit.qi.reference.directive.matches.expression_semantics"></a></span><a class="link" href="matches.html#spirit.qi.reference.directive.matches.expression_semantics">Expression 87 Semantics</a> 88 </h6> 89<p> 90 Semantics of an expression is defined only where it differs from, or 91 is not defined in <a class="link" href="../parser_concepts/unaryparser.html" title="UnaryParser"><code class="computeroutput"><span class="identifier">UnaryParser</span></code></a>. 92 </p> 93<div class="informaltable"><table class="table"> 94<colgroup> 95<col> 96<col> 97</colgroup> 98<thead><tr> 99<th> 100 <p> 101 Expression 102 </p> 103 </th> 104<th> 105 <p> 106 Semantics 107 </p> 108 </th> 109</tr></thead> 110<tbody><tr> 111<td> 112 <p> 113 <code class="computeroutput"><span class="identifier">matches</span><span class="special">[</span><span class="identifier">a</span><span class="special">]</span></code> 114 </p> 115 </td> 116<td> 117 <p> 118 Execute the subject parser <code class="computeroutput"><span class="identifier">a</span></code>, 119 and return as its attribute whether it succeeded. The directive 120 itself does always succeed. 121 </p> 122 </td> 123</tr></tbody> 124</table></div> 125<h6> 126<a name="spirit.qi.reference.directive.matches.h5"></a> 127 <span class="phrase"><a name="spirit.qi.reference.directive.matches.attributes"></a></span><a class="link" href="matches.html#spirit.qi.reference.directive.matches.attributes">Attributes</a> 128 </h6> 129<div class="informaltable"><table class="table"> 130<colgroup> 131<col> 132<col> 133</colgroup> 134<thead><tr> 135<th> 136 <p> 137 Expression 138 </p> 139 </th> 140<th> 141 <p> 142 Attribute 143 </p> 144 </th> 145</tr></thead> 146<tbody><tr> 147<td> 148 <p> 149 <code class="computeroutput"><span class="identifier">matches</span><span class="special">[</span><span class="identifier">a</span><span class="special">]</span></code> 150 </p> 151 </td> 152<td> 153 <p> 154 <code class="computeroutput"><span class="keyword">bool</span></code> 155 </p> 156 </td> 157</tr></tbody> 158</table></div> 159<h6> 160<a name="spirit.qi.reference.directive.matches.h6"></a> 161 <span class="phrase"><a name="spirit.qi.reference.directive.matches.complexity"></a></span><a class="link" href="matches.html#spirit.qi.reference.directive.matches.complexity">Complexity</a> 162 </h6> 163<div class="blockquote"><blockquote class="blockquote"><p> 164 The complexity is defined by the complexity of the subject parser, 165 <code class="computeroutput"><span class="identifier">a</span></code> 166 </p></blockquote></div> 167<h6> 168<a name="spirit.qi.reference.directive.matches.h7"></a> 169 <span class="phrase"><a name="spirit.qi.reference.directive.matches.example"></a></span><a class="link" href="matches.html#spirit.qi.reference.directive.matches.example">Example</a> 170 </h6> 171<div class="note"><table border="0" summary="Note"> 172<tr> 173<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../images/note.png"></td> 174<th align="left">Note</th> 175</tr> 176<tr><td align="left" valign="top"><p> 177 The test harness for the example(s) below is presented in the <a class="link" href="../basics.html#spirit.qi.reference.basics.examples">Basics Examples</a> 178 section. 179 </p></td></tr> 180</table></div> 181<p> 182 Some using declarations: 183 </p> 184<p> 185</p> 186<pre class="programlisting"><span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">qi</span><span class="special">::</span><span class="identifier">matches</span><span class="special">;</span> 187<span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">qi</span><span class="special">::</span><span class="identifier">int_</span><span class="special">;</span> 188</pre> 189<p> 190 </p> 191<p> 192 This parser tries to match an <code class="computeroutput"><span class="keyword">int</span></code> 193 and returns <code class="computeroutput"><span class="keyword">true</span></code> a its attribute 194 as it succeeded matching: 195 </p> 196<p> 197</p> 198<pre class="programlisting"><span class="keyword">bool</span> <span class="identifier">result</span> <span class="special">=</span> <span class="keyword">false</span><span class="special">;</span> 199<span class="identifier">test_parser_attr</span><span class="special">(</span><span class="string">"345"</span><span class="special">,</span> <span class="identifier">matches</span><span class="special">[</span><span class="identifier">int_</span><span class="special">],</span> <span class="identifier">result</span><span class="special">);</span> 200<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">boolalpha</span> <span class="special"><<</span> <span class="identifier">result</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> <span class="comment">// should print: true</span> 201</pre> 202<p> 203 </p> 204<p> 205 This parser tries to match an <code class="computeroutput"><span class="keyword">int</span></code> 206 as well and returns <code class="computeroutput"><span class="keyword">false</span></code> 207 as its attribute as it fails matching: 208 </p> 209<p> 210</p> 211<pre class="programlisting"><span class="identifier">result</span> <span class="special">=</span> <span class="keyword">true</span><span class="special">;</span> 212<span class="identifier">test_parser_attr</span><span class="special">(</span><span class="string">"abc"</span><span class="special">,</span> <span class="identifier">matches</span><span class="special">[</span><span class="identifier">int_</span><span class="special">],</span> <span class="identifier">result</span><span class="special">);</span> 213<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">boolalpha</span> <span class="special"><<</span> <span class="identifier">result</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> <span class="comment">// should print: false</span> 214</pre> 215<p> 216 </p> 217</div> 218<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 219<td align="left"></td> 220<td align="right"><div class="copyright-footer">Copyright © 2001-2011 Joel de Guzman, Hartmut Kaiser<p> 221 Distributed under the Boost Software License, Version 1.0. (See accompanying 222 file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 223 </p> 224</div></td> 225</tr></table> 226<hr> 227<div class="spirit-nav"> 228<a accesskey="p" href="repeat.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../directive.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="skip.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 229</div> 230</body> 231</html> 232
