ceph/src/boost/libs/mpl/doc/refmanual/always.html

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   7 <title>The MPL Reference Manual: always</title>
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  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>
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  14 <div class="section" id="always">
  15 <h1><a class="toc-backref" href="./miscellaneous.html#id1565">always</a></h1>
  16 <div class="section" id="id1155">
  17 <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
  18 <pre class="literal-block">
  19 template&lt;
  20       typename X
  21     &gt;
  22 struct <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="id1156">
  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 internal" href="./metafunction-class.html">Metafunction Class</a> always returning the
  32 same 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="id1157">
  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="id1158">
  41 <h3><a class="subsection-title" href="#model-of" name="model-of">Model of</a></h3>
  42 <p><a class="reference internal" href="./metafunction-class.html">Metafunction Class</a></p>
  43 </div>
  44 <div class="section" id="id1159">
  45 <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3>
  46 <table border="1" class="docutils table">
  47 <colgroup>
  48 <col width="22%" />
  49 <col width="28%" />
  50 <col width="51%" />
  51 </colgroup>
  52 <thead valign="bottom">
  53 <tr><th class="head">Parameter</th>
  54 <th class="head">Requirement</th>
  55 <th class="head">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="id1160">
  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">
  70 typedef <a href="./always.html" class="identifier">always</a>&lt;x&gt; f;
  71 </pre>
  72 <table class="docutils 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"><p class="first"><a class="reference internal" href="./metafunction-class.html">Metafunction Class</a>.</p>
  77 </td>
  78 </tr>
  79 <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p>
  80 <pre class="last literal-block">
  81 struct f : <a href="./bind.html" class="identifier">bind</a>&lt; <a href="./identity.html" class="identifier">identity</a>&lt;<a href="./placeholders.html" class="identifier">_1</a>&gt;, x > {};
  82 </pre>
  83 </td>
  84 </tr>
  85 </tbody>
  86 </table>
  87 </div>
  88 <div class="section" id="id1161">
  89 <h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
  90 <pre class="literal-block">
  91 typedef <a href="./always.html" class="identifier">always</a>&lt;<a href="./bool.html" class="identifier">true_</a>&gt; always_true;
  92
  93 <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./apply.html" class="identifier">apply</a>&lt; always_true,<a href="./bool.html" class="identifier">false_</a>&gt; ));
  94 <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./apply.html" class="identifier">apply</a>&lt; always_true,<a href="./bool.html" class="identifier">false_</a>,<a href="./bool.html" class="identifier">false_</a> &gt; ));
  95 <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./apply.html" class="identifier">apply</a>&lt; always_true,<a href="./bool.html" class="identifier">false_</a>,<a href="./bool.html" class="identifier">false_</a>,<a href="./bool.html" class="identifier">false_</a> > ));
  96 </pre>
  97 </div>
  98 <div class="section" id="id1162">
  99 <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
 100 <p><a class="reference internal" href="./metafunctions.html">Metafunctions</a>, <a class="reference internal" href="./metafunction-class.html">Metafunction Class</a>, <a class="reference internal" href="./identity.html">identity</a>, <a class="reference internal" href="./bind.html">bind</a>, <a class="reference internal" href="./apply.html">apply</a></p>
 101 <!-- Metafunctions/Miscellaneous//inherit |30 -->
 102 </div>
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