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<html>
<head>
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<title>Determine if a Type is a Character</title>
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<div class="section">
<div class="titlepage"><div><div><h5 class="title">
<a name="spirit.advanced.customize.string_traits.is_char"></a><a class="link" href="is_char.html" title="Determine if a Type is a Character">Determine
if a Type is a Character</a>
</h5></div></div></div>
<h6>
<a name="spirit.advanced.customize.string_traits.is_char.h0"></a>
<span><a name="spirit.advanced.customize.string_traits.is_char.is_char"></a></span><a class="link" href="is_char.html#spirit.advanced.customize.string_traits.is_char.is_char">is_char</a>
</h6>
<p>
<code class="computeroutput"><span class="identifier">is_char</span></code> is a metafunction
that detects if a given type is a character.
</p>
<h6>
<a name="spirit.advanced.customize.string_traits.is_char.h1"></a>
<span><a name="spirit.advanced.customize.string_traits.is_char.module_headers"></a></span><a class="link" href="is_char.html#spirit.advanced.customize.string_traits.is_char.module_headers">Module
Headers</a>
</h6>
<pre class="programlisting"><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">home</span><span class="special">/</span><span class="identifier">support</span><span class="special">/</span><span class="identifier">string_traits</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>
<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>
This header file does not need to be included directly by any user
program as it is normally included by other Spirit header files relying
on its content.
</p></td></tr>
</table></div>
<h6>
<a name="spirit.advanced.customize.string_traits.is_char.h2"></a>
<span><a name="spirit.advanced.customize.string_traits.is_char.namespace"></a></span><a class="link" href="is_char.html#spirit.advanced.customize.string_traits.is_char.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">traits</span></code>
</p>
</td></tr></tbody>
</table></div>
<h6>
<a name="spirit.advanced.customize.string_traits.is_char.h3"></a>
<span><a name="spirit.advanced.customize.string_traits.is_char.synopsis"></a></span><a class="link" href="is_char.html#spirit.advanced.customize.string_traits.is_char.synopsis">Synopsis</a>
</h6>
<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">></span>
<span class="keyword">struct</span> <span class="identifier">is_char</span>
<span class="special">{</span>
<span class="special"><</span><span class="identifier">unspecified</span><span class="special">>;</span>
<span class="special">};</span>
</pre>
<h6>
<a name="spirit.advanced.customize.string_traits.is_char.h4"></a>
<span><a name="spirit.advanced.customize.string_traits.is_char.template_parameters"></a></span><a class="link" href="is_char.html#spirit.advanced.customize.string_traits.is_char.template_parameters">Template
parameters</a>
</h6>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Parameter
</p>
</th>
<th>
<p>
Description
</p>
</th>
<th>
<p>
Default
</p>
</th>
</tr></thead>
<tbody><tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">T</span></code>
</p>
</td>
<td>
<p>
The type to detect.
</p>
</td>
<td>
<p>
none
</p>
</td>
</tr></tbody>
</table></div>
<div class="variablelist">
<p class="title"><b>Notation</b></p>
<dl>
<dt><span class="term"><code class="computeroutput"><span class="identifier">T</span></code></span></dt>
<dd><p>
An arbitrary type
</p></dd>
</dl>
</div>
<h6>
<a name="spirit.advanced.customize.string_traits.is_char.h5"></a>
<span><a name="spirit.advanced.customize.string_traits.is_char.expression_semantics"></a></span><a class="link" href="is_char.html#spirit.advanced.customize.string_traits.is_char.expression_semantics">Expression
Semantics</a>
</h6>
<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">is_char</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">type</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span></code> if T should be treated
as a character type, and <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">false_</span></code>
otherwise. Generally, any implementation of <code class="computeroutput"><span class="identifier">is_char</span></code>
needs to behave as if if was a <a href="../../../../../../../../libs/mpl/doc/refmanual/integral-constant.html" target="_top">MPL
Boolean Constant</a>.
</p>
</td>
</tr></tbody>
</table></div>
<h6>
<a name="spirit.advanced.customize.string_traits.is_char.h6"></a>
<span><a name="spirit.advanced.customize.string_traits.is_char.predefined_specializations"></a></span><a class="link" href="is_char.html#spirit.advanced.customize.string_traits.is_char.predefined_specializations">Predefined
Specializations</a>
</h6>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Type
</p>
</th>
<th>
<p>
Semantics
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">T</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">false_</span></code>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="identifier">is_char</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="keyword">char</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span></code>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="keyword">wchar_t</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span></code>
</p>
</td>
</tr>
</tbody>
</table></div>
<h6>
<a name="spirit.advanced.customize.string_traits.is_char.h7"></a>
<span><a name="spirit.advanced.customize.string_traits.is_char.when_to_implement"></a></span><a class="link" href="is_char.html#spirit.advanced.customize.string_traits.is_char.when_to_implement">When
to implement</a>
</h6>
<p>
This customization point needs to be implemented for any strings that
use a type other than <code class="computeroutput"><span class="keyword">char</span></code>
or `wchar_t to store character data.
</p>
<h6>
<a name="spirit.advanced.customize.string_traits.is_char.h8"></a>
<span><a name="spirit.advanced.customize.string_traits.is_char.related_attribute_customization_points"></a></span><a class="link" href="is_char.html#spirit.advanced.customize.string_traits.is_char.related_attribute_customization_points">Related
Attribute Customization Points</a>
</h6>
<p>
If this customization point is implemented, the following other customization
points need to be implemented as well.
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Name
</p>
</th>
<th>
<p>
When to implement
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<a class="link" href="../is_string.html" title="Determine if a Type Should be Treated as a String (Qi and Karma)"><code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">is_string</span></code></a>
</p>
</td>
<td>
<p>
Whenever <code class="computeroutput"><span class="identifier">is_char</span></code>
is implemented.
</p>
</td>
</tr>
<tr>
<td>
<p>
<a class="link" href="char_type_of.html" title="Determine the Character Type of a String"><code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">char_type_of</span></code></a>
</p>
</td>
<td>
<p>
Whenever <code class="computeroutput"><span class="identifier">is_char</span></code>
is implemented.
</p>
</td>
</tr>
</tbody>
</table></div>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright © 2001-2011 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>)
</p>
</div></td>
</tr></table>
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