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Aleksey Gurtovoy 203a9f086a merge RC_1_32_0 fixes 
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<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="generator" content="Docutils 0.3.6: http://docutils.sourceforge.net/" />
<title>The MPL Reference Manual: if_</title>
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<body class="docframe refmanual">
<table class="header"><tr class="header"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./type-selection.html" class="navigation-link">Prev</a>&nbsp;<a href="./if-c.html" class="navigation-link">Next</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group">Back&nbsp;<a href="./if-c.html" class="navigation-link">Along</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./type-selection.html" class="navigation-link">Up</a>&nbsp;<a href="../refmanual.html" class="navigation-link">Home</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./refmanual_toc.html" class="navigation-link">Full TOC</a></span></td>
<td class="header-group page-location"><a href="../refmanual.html" class="navigation-link">Front Page</a> / <a href="./metafunctions.html" class="navigation-link">Metafunctions</a> / <a href="./type-selection.html" class="navigation-link">Type Selection</a> / <a href="./if.html" class="navigation-link">if_</a></td>
</tr></table><div class="header-separator"></div>
<div class="section" id="if">
<h1><a class="toc-backref" href="./type-selection.html#id446" name="if">if_</a></h1>
<div class="section" id="if-synopsis">
<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
<pre class="literal-block">
template&lt;
typename C
, typename T1
, typename T2
&gt;
struct <a href="./if.html" class="identifier">if_</a>
{
typedef <em>unspecified</em> type;
};
</pre>
</div>
<div class="section" id="if-description">
<h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
<p>Returns one of its two arguments, <tt class="literal"><span class="pre">T1</span></tt> or <tt class="literal"><span class="pre">T2</span></tt>, depending on the value <tt class="literal"><span class="pre">C</span></tt>.</p>
</div>
<div class="section" id="if-header">
<h3><a class="subsection-title" href="#header" name="header">Header</a></h3>
<pre class="literal-block">
#include &lt;<a href="../../../../boost/mpl/if.hpp" class="header">boost/mpl/if.hpp</a>&gt;
</pre>
</div>
<div class="section" id="if-parameters">
<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3>
<table border="1" class="table">
<colgroup>
<col width="15%" />
<col width="36%" />
<col width="48%" />
</colgroup>
<thead valign="bottom">
<tr><th>Parameter</th>
<th>Requirement</th>
<th>Description</th>
</tr>
</thead>
<tbody valign="top">
<tr><td><tt class="literal"><span class="pre">C</span></tt></td>
<td><a class="reference" href="./integral-constant.html">Integral Constant</a></td>
<td>A selection condition.</td>
</tr>
<tr><td><tt class="literal"><span class="pre">T1</span></tt>, <tt class="literal"><span class="pre">T2</span></tt></td>
<td>Any type</td>
<td>Types to select from.</td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="if-expression-semantics">
<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
<p>For any <a class="reference" href="./integral-constant.html">Integral Constant</a> <tt class="literal"><span class="pre">c</span></tt> and arbitrary types <tt class="literal"><span class="pre">t1</span></tt>, <tt class="literal"><span class="pre">t2</span></tt>:</p>
<pre class="literal-block">
typedef <a href="./if.html" class="identifier">if_</a>&lt;c,t1,t2&gt;::type t;
</pre>
<table class="field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Return type:</th><td class="field-body">Any type.</td>
</tr>
<tr class="field"><th class="field-name">Semantics:</th><td class="field-body">If <tt class="literal"><span class="pre">c::value</span> <span class="pre">==</span> <span class="pre">true</span></tt>, <tt class="literal"><span class="pre">t</span></tt> is identical to <tt class="literal"><span class="pre">t1</span></tt>; otherwise <tt class="literal"><span class="pre">t</span></tt> is
identical to <tt class="literal"><span class="pre">t2</span></tt>.</td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="if-example">
<h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
<pre class="literal-block">
typedef <a href="./if.html" class="identifier">if_</a>&lt;true_,char,long&gt;::type t1;
typedef <a href="./if.html" class="identifier">if_</a>&lt;false_,char,long&gt;::type t2;
<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same&lt;t1, char&gt; ));
<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same&lt;t2, long&gt; ));
</pre>
</div>
<div class="section" id="if-see-also">
<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
<p><a class="reference" href="./metafunctions.html">Metafunctions</a>, <a class="reference" href="./integral-constant.html">Integral Constant</a>, <a class="refentry reference" href="./if-c.html"><tt class="refentry literal"><span class="pre">if_c</span></tt></a>, <a class="refentry reference" href="./eval-if.html"><tt class="refentry literal"><span class="pre">eval_if</span></tt></a></p>
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