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<div class="titlepage"><div><div><h5 class="title">
<a name="spirit.qi.reference.directive.matches"></a><a class="link" href="matches.html" title="Test if Parser Succeeded (matches[])"> Test if Parser
Succeeded (<code class="computeroutput"><span class="identifier">matches</span><span class="special">[]</span></code>)</a>
</h5></div></div></div>
<a name="spirit.qi.reference.directive.matches.description"></a><h6>
<a name="id938266"></a>
<a class="link" href="matches.html#spirit.qi.reference.directive.matches.description">Description</a>
</h6>
<p>
The <code class="computeroutput"><span class="identifier">matches</span><span class="special">[]</span></code>
directive executes the embedded parser and returns whether it succeeded
matching.
</p>
<a name="spirit.qi.reference.directive.matches.header"></a><h6>
<a name="id938293"></a>
<a class="link" href="matches.html#spirit.qi.reference.directive.matches.header">Header</a>
</h6>
<pre class="programlisting"><span class="comment">// forwards to <boost/spirit/home/qi/directive/matches.hpp>
</span><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>
</pre>
<p>
Also, see <a class="link" href="../../../structure/include.html" title="Include">Include Structure</a>.
</p>
<a name="spirit.qi.reference.directive.matches.namespace"></a><h6>
<a name="id938368"></a>
<a class="link" href="matches.html#spirit.qi.reference.directive.matches.namespace">Namespace</a>
</h6>
<div class="informaltable"><table class="table">
<colgroup><col></colgroup>
<thead><tr><th>
<p>
Name
</p>
</th></tr></thead>
<tbody><tr><td>
<p>
<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">//
alias: boost::spirit::qi::matches</span></code>
</p>
</td></tr></tbody>
</table></div>
<a name="spirit.qi.reference.directive.matches.model_of"></a><h6>
<a name="id938447"></a>
<a class="link" href="matches.html#spirit.qi.reference.directive.matches.model_of">Model
of</a>
</h6>
<div class="blockquote"><blockquote class="blockquote"><p>
<a class="link" href="../parser_concepts/unaryparser.html" title="UnaryParser"><code class="computeroutput"><span class="identifier">UnaryParser</span></code></a>
</p></blockquote></div>
<div class="variablelist">
<p class="title"><b>Notation</b></p>
<dl>
<dt><span class="term"><code class="computeroutput"><span class="identifier">a</span></code></span></dt>
<dd><p>
A <a class="link" href="../parser_concepts/parser.html" title="Parser"><code class="computeroutput"><span class="identifier">Parser</span></code></a>.
</p></dd>
</dl>
</div>
<a name="spirit.qi.reference.directive.matches.expression_semantics"></a><h6>
<a name="id938515"></a>
<a class="link" href="matches.html#spirit.qi.reference.directive.matches.expression_semantics">Expression
Semantics</a>
</h6>
<p>
Semantics of an expression is defined only where it differs from, or
is not defined in <a class="link" href="../parser_concepts/unaryparser.html" title="UnaryParser"><code class="computeroutput"><span class="identifier">UnaryParser</span></code></a>.
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Expression
</p>
</th>
<th>
<p>
Semantics
</p>
</th>
</tr></thead>
<tbody><tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">matches</span><span class="special">[</span><span class="identifier">a</span><span class="special">]</span></code>
</p>
</td>
<td>
<p>
Execute the subject parser <code class="computeroutput"><span class="identifier">a</span></code>,
and return as its attribute whether it succeeded. The directive
itself does always succeed.
</p>
</td>
</tr></tbody>
</table></div>
<a name="spirit.qi.reference.directive.matches.attributes"></a><h6>
<a name="id938622"></a>
<a class="link" href="matches.html#spirit.qi.reference.directive.matches.attributes">Attributes</a>
</h6>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Expression
</p>
</th>
<th>
<p>
Attribute
</p>
</th>
</tr></thead>
<tbody><tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">matches</span><span class="special">[</span><span class="identifier">a</span><span class="special">]</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="keyword">bool</span></code>
</p>
</td>
</tr></tbody>
</table></div>
<a name="spirit.qi.reference.directive.matches.complexity"></a><h6>
<a name="id938713"></a>
<a class="link" href="matches.html#spirit.qi.reference.directive.matches.complexity">Complexity</a>
</h6>
<div class="blockquote"><blockquote class="blockquote"><p>
The complexity is defined by the complexity of the subject parser,
<code class="computeroutput"><span class="identifier">a</span></code>
</p></blockquote></div>
<a name="spirit.qi.reference.directive.matches.example"></a><h6>
<a name="id938741"></a>
<a class="link" href="matches.html#spirit.qi.reference.directive.matches.example">Example</a>
</h6>
<div class="note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top"><p>
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>
section.
</p></td></tr>
</table></div>
<p>
Some using declarations:
</p>
<p>
</p>
<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>
<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>
</pre>
<p>
</p>
<p>
This parser tries to match an <code class="computeroutput"><span class="keyword">int</span></code>
and returns <code class="computeroutput"><span class="keyword">true</span></code> a its attribute
as it succeeded matching:
</p>
<p>
</p>
<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>
<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>
<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></pre>
<p>
</p>
<p>
This parser tries to match an <code class="computeroutput"><span class="keyword">int</span></code>
as well and returns <code class="computeroutput"><span class="keyword">false</span></code>
as its attribute as it fails matching:
</p>
<p>
</p>
<pre class="programlisting"><span class="identifier">result</span> <span class="special">=</span> <span class="keyword">true</span><span class="special">;</span>
<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>
<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></pre>
<p>
</p>
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<td align="right"><div class="copyright-footer">Copyright © 2001-2010 Joel de Guzman, Hartmut Kaiser<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
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>)
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