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

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  14 <div class="section" id="arg">
  15 <h1><a class="toc-backref" href="./composition-and-argument-binding.html#id1533">arg</a></h1>
  16 <div class="section" id="id946">
  17 <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
  18 <pre class="literal-block">
  19 template&lt; int n &gt; struct <a href="./arg.html" class="identifier">arg</a>;
  20
  21 template&lt;&gt; struct <a href="./arg.html" class="identifier">arg</a>&lt;1&gt;
  22 {
  23     template&lt; typename A1,<em>...</em> typename A<em>n</em> = <em>unspecified</em> &gt;
  24     struct <a href="./apply.html" class="identifier">apply</a>
  25     {
  26         typedef A1 type;
  27     };
  28 };
  29
  30 <em>...</em>
  31
  32 template&lt;&gt; struct <a href="./arg.html" class="identifier">arg</a>&lt;<em>n</em>&gt;
  33 {
  34     template&lt; typename A1,<em>...</em> typename A<em>n</em> &gt;
  35     struct <a href="./apply.html" class="identifier">apply</a>
  36     {
  37         typedef A<em>n</em> type;
  38     };
  39 };
  40 </pre>
  41 </div>
  42 <div class="section" id="id947">
  43 <h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
  44 <p><tt class="literal"><span class="pre"><a href="./arg.html" class="identifier">arg</a>&lt;n&gt;</span></tt> specialization is a <a class="reference internal" href="./metafunction-class.html">Metafunction Class</a> that return the <tt class="literal"><span class="pre">n</span></tt>th of its arguments.</p>
  45 </div>
  46 <div class="section" id="id948">
  47 <h3><a class="subsection-title" href="#header" name="header">Header</a></h3>
  48 <pre class="literal-block">
  49 #include &lt;<a href="../../../../boost/mpl/arg.hpp" class="header">boost/mpl/arg.hpp</a>&gt;
  50 </pre>
  51 </div>
  52 <div class="section" id="id949">
  53 <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3>
  54 <table border="1" class="docutils table">
  55 <colgroup>
  56 <col width="15%" />
  57 <col width="36%" />
  58 <col width="48%" />
  59 </colgroup>
  60 <thead valign="bottom">
  61 <tr><th class="head">Parameter</th>
  62 <th class="head">Requirement</th>
  63 <th class="head">Description</th>
  64 </tr>
  65 </thead>
  66 <tbody valign="top">
  67 <tr><td><tt class="literal"><span class="pre">n</span></tt></td>
  68 <td>An integral constant</td>
  69 <td>A number of argument to return.</td>
  70 </tr>
  71 </tbody>
  72 </table>
  73 </div>
  74 <div class="section" id="id950">
  75 <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
  76 <p>For any integral constant <tt class="literal"><span class="pre">n</span></tt> in the range [1, <a class="reference internal" href="./limit-metafunction-arity.html">BOOST_MPL_LIMIT_METAFUNCTION_ARITY</a>] and
  77 arbitrary types <tt class="literal"><span class="pre">a1</span></tt>,... <tt class="literal"><span class="pre">an</span></tt>:</p>
  78 <pre class="literal-block">
  79 typedef <a href="./apply-wrap.html" class="identifier">apply_wrap</a><em>n</em>&lt; <a href="./arg.html" class="identifier">arg</a>&lt;<em>n</em>&gt;,a1,<em>...</em>a<em>n</em> &gt;::type x;
  80 </pre>
  81 <table class="docutils field-list" frame="void" rules="none">
  82 <col class="field-name" />
  83 <col class="field-body" />
  84 <tbody valign="top">
  85 <tr class="field"><th class="field-name">Return type:</th><td class="field-body">A type.</td>
  86 </tr>
  87 <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><tt class="literal"><span class="pre">x</span></tt> is identical to <tt class="literal"><span class="pre">an</span></tt>.</td>
  88 </tr>
  89 </tbody>
  90 </table>
  91 </div>
  92 <div class="section" id="id951">
  93 <h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
  94 <pre class="literal-block">
  95 typedef <a href="./apply-wrap.html" class="identifier">apply_wrap</a><tt class="literal"><span class="pre">5</span></tt>&lt; <a href="./arg.html" class="identifier">arg</a>&lt;1&gt;,bool,char,short,int,long &gt;::type t1;
  96 typedef <a href="./apply-wrap.html" class="identifier">apply_wrap</a><tt class="literal"><span class="pre">5</span></tt>&lt; <a href="./arg.html" class="identifier">arg</a>&lt;3&gt;,bool,char,short,int,long &gt;::type t3;
  97
  98 <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same&lt; t1, bool &gt; ));
  99 <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same&lt; t3, short > ));
 100 </pre>
 101 </div>
 102 <div class="section" id="id952">
 103 <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
 104 <p><a class="reference internal" href="./composition-and-argument-binding.html">Composition and Argument Binding</a>, <a class="reference internal" href="./placeholders.html">Placeholders</a>, <a class="reference internal" href="./lambda.html">lambda</a>, <a class="reference internal" href="./bind.html">bind</a>, <a class="reference internal" href="./apply.html">apply</a>, <a class="reference internal" href="./apply-wrap.html">apply_wrap</a></p>
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