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6<meta name="generator" content="Docutils 0.3.6: http://docutils.sourceforge.net/" />
7<title>The MPL Reference Manual: always</title>
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11<table class="header"><tr class="header"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./identity.html" class="navigation-link">Prev</a>&nbsp;<a href="./inherit.html" class="navigation-link">Next</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./identity.html" class="navigation-link">Back</a>&nbsp;<a href="./inherit.html" class="navigation-link">Along</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./miscellaneous.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>
12<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="./miscellaneous.html" class="navigation-link">Miscellaneous</a> / <a href="./always.html" class="navigation-link">always</a></td>
13</tr></table><div class="header-separator"></div>
14<div class="section" id="always">
15<h1><a class="toc-backref" href="./miscellaneous.html#id489" name="always">always</a></h1>
16<div class="section" id="always-synopsis">
17<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
18<pre class="literal-block">
19template&lt; 
20      typename X
21    &gt;
22struct <a href="./always.html" class="identifier">always</a>
23{
24    // <em>unspecified</em>
25    // <em>...</em>
26};
27</pre>
28</div>
29<div class="section" id="always-description">
30<h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
31<p><tt class="literal"><span class="pre"><a href="./always.html" class="identifier">always</a>&lt;X&gt;</span></tt> specialization is a variadic <a class="reference" href="./metafunction-class.html">Metafunction Class</a> always returning the
32same type, <tt class="literal"><span class="pre">X</span></tt>, regardless of the number and types of passed arguments.</p>
33</div>
34<div class="section" id="always-header">
35<h3><a class="subsection-title" href="#header" name="header">Header</a></h3>
36<pre class="literal-block">
37#include &lt;<a href="../../../../boost/mpl/always.hpp" class="header">boost/mpl/always.hpp</a>&gt;
38</pre>
39</div>
40<div class="section" id="always-model-of">
41<h3><a class="subsection-title" href="#model-of" name="model-of">Model of</a></h3>
42<p><a class="reference" href="./metafunction-class.html">Metafunction Class</a></p>
43</div>
44<div class="section" id="always-parameters">
45<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3>
46<table border="1" class="table">
47<colgroup>
48<col width="22%" />
49<col width="28%" />
50<col width="51%" />
51</colgroup>
52<thead valign="bottom">
53<tr><th>Parameter</th>
54<th>Requirement</th>
55<th>Description</th>
56</tr>
57</thead>
58<tbody valign="top">
59<tr><td><tt class="literal"><span class="pre">X</span></tt></td>
60<td>Any type</td>
61<td>A type to be returned.</td>
62</tr>
63</tbody>
64</table>
65</div>
66<div class="section" id="always-expression-semantics">
67<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
68<p>For an arbitrary type <tt class="literal"><span class="pre">x</span></tt>:</p>
69<pre class="literal-block">
70typedef <a href="./always.html" class="identifier">always</a>&lt;x&gt; f;
71</pre>
72<table class="field-list" frame="void" rules="none">
73<col class="field-name" />
74<col class="field-body" />
75<tbody valign="top">
76<tr class="field"><th class="field-name">Return type:</th><td class="field-body"><a class="reference" href="./metafunction-class.html">Metafunction Class</a>.</td>
77</tr>
78<tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p>
79<pre class="last literal-block">
80struct f : <a href="./bind.html" class="identifier">bind</a>&lt; <a href="./identity.html" class="identifier">identity</a>&lt;_1&gt;, x > {};
81</pre>
82</td>
83</tr>
84</tbody>
85</table>
86</div>
87<div class="section" id="always-example">
88<h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
89<pre class="literal-block">
90typedef <a href="./always.html" class="identifier">always</a>&lt;true_&gt; always_true;
91
92<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./apply.html" class="identifier">apply</a>&lt; always_true,false_&gt; ));
93<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./apply.html" class="identifier">apply</a>&lt; always_true,false_,false_ &gt; ));
94<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./apply.html" class="identifier">apply</a>&lt; always_true,false_,false_,false_ > ));
95</pre>
96</div>
97<div class="section" id="always-see-also">
98<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
99<p><a class="reference" href="./metafunctions.html">Metafunctions</a>, <a class="reference" href="./metafunction-class.html">Metafunction Class</a>, <a class="refentry reference" href="./identity.html"><tt class="refentry literal"><span class="pre">identity</span></tt></a>, <a class="refentry reference" href="./bind.html"><tt class="refentry literal"><span class="pre">bind</span></tt></a>, <a class="refentry reference" href="./apply.html"><tt class="refentry literal"><span class="pre">apply</span></tt></a></p>
100<!-- modtime: November 13, 2004 02:52:37 +0000 -->
101<!-- Metafunctions/Miscellaneous//inherit |30 -->
102</div>
103</div>
104
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