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updated boost from 1_33_1 to 1_34_1
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14<table class="header"><tr class="header"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./if.html" class="navigation-link">Prev</a>&nbsp;<a href="./eval-if.html" class="navigation-link">Next</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./if.html" class="navigation-link">Back</a>&nbsp;<a href="./eval-if.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>
15<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-c.html" class="navigation-link">if_c</a></td>
16</tr></table><div class="header-separator"></div>
17<div class="section" id="if-c">
18<h1><a class="toc-backref" href="./type-selection.html#id447" name="if-c">if_c</a></h1>
19<div class="section" id="type-if-synopsis">
20<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
21<pre class="literal-block">
22template&lt; 
23      bool c
24    , typename T1
25    , typename T2
26    &gt;
27struct <a href="./if-c.html" class="identifier">if_c</a>
28{
29    typedef <em>unspecified</em> type;
30};
31</pre>
32</div>
33<div class="section" id="type-if-description">
34<h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
35<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 of
36integral constant <tt class="literal"><span class="pre">c</span></tt>. <tt class="literal"><span class="pre"><a href="./if-c.html" class="identifier">if_c</a>&lt;c,t1,t2&gt;::type</span></tt> is a shorcut notation for
37<tt class="literal"><span class="pre"><a href="./if.html" class="identifier">if_</a>&lt;</span> <span class="pre"><a href="./bool.html" class="identifier">bool_</a>&lt;c&gt;,t1,t2</span> <span class="pre">&gt;::type</span></tt>.</p>
38</div>
39<div class="section" id="type-if-header">
40<h3><a class="subsection-title" href="#header" name="header">Header</a></h3>
41<pre class="literal-block">
42#include &lt;<a href="../../../../boost/mpl/if.hpp" class="header">boost/mpl/if.hpp</a>&gt;
43</pre>
44</div>
45<div class="section" id="type-if-parameters">
46<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3>
47<table border="1" class="table">
48<colgroup>
49<col width="15%" />
50<col width="36%" />
51<col width="48%" />
52</colgroup>
53<thead valign="bottom">
54<tr><th>Parameter</th>
55<th>Requirement</th>
56<th>Description</th>
57</tr>
58</thead>
59<tbody valign="top">
60<tr><td><tt class="literal"><span class="pre">c</span></tt></td>
61<td>An integral constant</td>
62<td>A selection condition.</td>
63</tr>
64<tr><td><tt class="literal"><span class="pre">T1</span></tt>, <tt class="literal"><span class="pre">T2</span></tt></td>
65<td>Any type</td>
66<td>Types to select from.</td>
67</tr>
68</tbody>
69</table>
70</div>
71<div class="section" id="type-if-expression-semantics">
72<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
73<p>For any integral constant <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>
74<pre class="literal-block">
75typedef <a href="./if-c.html" class="identifier">if_c</a>&lt;c,t1,t2&gt;::type t;
76</pre>
77<table class="field-list" frame="void" rules="none">
78<col class="field-name" />
79<col class="field-body" />
80<tbody valign="top">
81<tr class="field"><th class="field-name">Return type:</th><td class="field-body">Any type.</td>
82</tr>
83<tr class="field"><th class="field-name">Semantics:</th><td class="field-body">Equivalent to <tt class="literal"><span class="pre">typedef</span> <span class="pre"><a href="./if.html" class="identifier">if_</a>&lt;</span> <span class="pre"><a href="./bool.html" class="identifier">bool_</a>&lt;c&gt;,t1,t2</span> <span class="pre">&gt;::type</span> <span class="pre">t;</span></tt></td>
84</tr>
85</tbody>
86</table>
87</div>
88<div class="section" id="type-if-example">
89<h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
90<pre class="literal-block">
91typedef <a href="./if-c.html" class="identifier">if_c</a>&lt;true,char,long&gt;::type t1;
92typedef <a href="./if-c.html" class="identifier">if_c</a>&lt;false,char,long&gt;::type t2;
93
94<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same&lt;t1, char&gt; ));
95<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same&lt;t2, long&gt; ));
96</pre>
97</div>
98<div class="section" id="type-if-see-also">
99<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
100<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.html"><tt class="refentry literal"><span class="pre">if_</span></tt></a>, <a class="refentry reference" href="./eval-if.html"><tt class="refentry literal"><span class="pre">eval_if</span></tt></a>, <a class="refentry reference" href="./bool.html"><tt class="refentry literal"><span class="pre">bool_</span></tt></a></p>
101<!-- modtime: November 10, 2004 04:40:22 +0000 -->
102<!-- Metafunctions/Type Selection//eval_if |30 -->
103</div>
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