ceph/src/boost/libs/mpl/doc/refmanual/metafunction-class.html

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   7 <title>The MPL Reference Manual: Metafunction Class</title>
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  11 <table class="header"><tr class="header"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./metafunction.html" class="navigation-link">Prev</a>&nbsp;<a href="./lambda-expression.html" class="navigation-link">Next</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./metafunction.html" class="navigation-link">Back</a>&nbsp;<a href="./lambda-expression.html" class="navigation-link">Along</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./metafunctions-concepts.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="./metafunctions-concepts.html" class="navigation-link">Concepts</a> / <a href="./metafunction-class.html" class="navigation-link">Metafunction Class</a></td>
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  14 <div class="section" id="metafunction-class">
  15 <h1><a class="toc-backref" href="./metafunctions-concepts.html#id1513">Metafunction Class</a></h1>
  16 <div class="section" id="summary">
  17 <h3>Summary</h3>
  18 <p>A <em>metafunction class</em> is a certain form of metafunction representation
  19 that enables higher-order metaprogramming. More precisely, it's a class
  20 with a publicly-accessible nested <a class="reference internal" href="./metafunction.html">Metafunction</a> called <tt class="literal"><span class="pre"><a href="./apply.html" class="identifier">apply</a></span></tt>.
  21 Correspondingly, a metafunction class invocation is defined as invocation
  22 of its nested <tt class="literal"><span class="pre"><a href="./apply.html" class="identifier">apply</a></span></tt> metafunction.</p>
  23 </div>
  24 <div class="section" id="id827">
  25 <h3><a class="subsection-title" href="#expression-requirements" name="expression-requirements">Expression requirements</a></h3>
  26 <p>In the following table and subsequent specifications, <tt class="literal"><span class="pre">f</span></tt> is a <a class="reference internal" href="./metafunction-class.html">Metafunction Class</a>.</p>
  27 <table border="1" class="docutils table">
  28 <colgroup>
  29 <col width="36%" />
  30 <col width="32%" />
  31 <col width="32%" />
  32 </colgroup>
  33 <thead valign="bottom">
  34 <tr><th class="head">Expression</th>
  35 <th class="head">Type</th>
  36 <th class="head">Complexity</th>
  37 </tr>
  38 </thead>
  39 <tbody valign="top">
  40 <tr><td><tt class="literal"><span class="pre">f::<a href="./apply.html" class="identifier">apply</a>::type</span></tt></td>
  41 <td>Any type</td>
  42 <td>Unspecified.</td>
  43 </tr>
  44 <tr><td><tt class="literal"><span class="pre">f::<a href="./apply.html" class="identifier">apply</a>&lt;&gt;::type</span></tt></td>
  45 <td>Any type</td>
  46 <td>Unspecified.</td>
  47 </tr>
  48 <tr><td><tt class="literal"><span class="pre">f::<a href="./apply.html" class="identifier">apply</a>&lt;a1,...an&gt;::type</span></tt></td>
  49 <td>Any type</td>
  50 <td>Unspecified.</td>
  51 </tr>
  52 </tbody>
  53 </table>
  54 </div>
  55 <div class="section" id="id828">
  56 <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
  57 <pre class="literal-block">
  58 typedef f::<a href="./apply.html" class="identifier">apply</a>::type x;
  59 </pre>
  60 <table class="docutils field-list" frame="void" rules="none">
  61 <col class="field-name" />
  62 <col class="field-body" />
  63 <tbody valign="top">
  64 <tr class="field"><th class="field-name">Precondition:</th><td class="field-body"><tt class="literal"><span class="pre">f</span></tt> is a nullary <a class="reference internal" href="./metafunction-class.html">Metafunction Class</a>; <tt class="literal"><span class="pre">f::<a href="./apply.html" class="identifier">apply</a>::type</span></tt> is a <em>type-name</em>.</td>
  65 </tr>
  66 <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><tt class="literal"><span class="pre">x</span></tt> is the result of the metafunction class invocation.</td>
  67 </tr>
  68 </tbody>
  69 </table>
  70 <!-- ................................................................................... -->
  71 <pre class="literal-block">
  72 typedef f::<a href="./apply.html" class="identifier">apply</a>&lt;&gt;::type x;
  73 </pre>
  74 <table class="docutils field-list" frame="void" rules="none">
  75 <col class="field-name" />
  76 <col class="field-body" />
  77 <tbody valign="top">
  78 <tr class="field"><th class="field-name">Precondition:</th><td class="field-body"><tt class="literal"><span class="pre">f</span></tt> is a nullary <a class="reference internal" href="./metafunction-class.html">Metafunction Class</a>; <tt class="literal"><span class="pre">f::<a href="./apply.html" class="identifier">apply</a>&lt;&gt;::type</span></tt> is a <em>type-name</em>.</td>
  79 </tr>
  80 <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><tt class="literal"><span class="pre">x</span></tt> is the result of the metafunction class invocation.</td>
  81 </tr>
  82 </tbody>
  83 </table>
  84 <!-- ................................................................................... -->
  85 <pre class="literal-block">
  86 typedef f::<a href="./apply.html" class="identifier">apply</a>&lt;a1,<em>...</em>a<em>n</em>&gt;::type x;
  87 </pre>
  88 <table class="docutils field-list" frame="void" rules="none">
  89 <col class="field-name" />
  90 <col class="field-body" />
  91 <tbody valign="top">
  92 <tr class="field"><th class="field-name">Precondition:</th><td class="field-body"><tt class="literal"><span class="pre">f</span></tt> is an <em>n</em>-ary metafunction class; <tt class="literal"><span class="pre"><a href="./apply.html" class="identifier">apply</a></span></tt> is a <a class="reference internal" href="./metafunction.html">Metafunction</a>.</td>
  93 </tr>
  94 <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><tt class="literal"><span class="pre">x</span></tt> is the result of the metafunction class
  95 invocation with the actual arguments <tt class="literal"><span class="pre">a1</span></tt>,... <tt class="literal"><span class="pre">an</span></tt>.</td>
  96 </tr>
  97 </tbody>
  98 </table>
  99 </div>
 100 <div class="section" id="id829">
 101 <h3><a class="subsection-title" href="#models" name="models">Models</a></h3>
 102 <ul class="simple">
 103 <li><a class="reference internal" href="./always.html">always</a></li>
 104 <li><a class="reference internal" href="./arg.html">arg</a></li>
 105 <li><a class="reference internal" href="./quote.html">quote</a></li>
 106 <li><a class="reference internal" href="./numeric-cast.html">numeric_cast</a></li>
 107 <li><a class="reference internal" href="./unpack-args.html">unpack_args</a></li>
 108 </ul>
 109 </div>
 110 <div class="section" id="id830">
 111 <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
 112 <p><a class="reference internal" href="./metafunctions.html">Metafunctions</a>, <a class="reference internal" href="./metafunction.html">Metafunction</a>, <a class="reference internal" href="./lambda-expression.html">Lambda Expression</a>, <a class="reference internal" href="./invocation.html">invocation</a>, <a class="reference internal" href="./apply-wrap.html">apply_wrap</a>, <a class="reference internal" href="./bind.html">bind</a>, <a class="reference internal" href="./quote.html">quote</a></p>
 113 <!-- Metafunctions/Concepts//Lambda Expression |30 -->
 114 </div>
 115 </div>
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