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

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   7 <title>The MPL Reference Manual: size</title>
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  12 <td class="header-group page-location"><a href="../refmanual.html" class="navigation-link">Front Page</a> / <a href="./sequences.html" class="navigation-link">Sequences</a> / <a href="./intrinsic-metafunctions.html" class="navigation-link">Intrinsic Metafunctions</a> / <a href="./size.html" class="navigation-link">size</a></td>
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  14 <div class="section" id="size">
  15 <h1><a class="toc-backref" href="./intrinsic-metafunctions.html#id1446">size</a></h1>
  16 <div class="section" id="id362">
  17 <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
  18 <pre class="literal-block">
  19 template&lt;
  20       typename Sequence
  21     &gt;
  22 struct <a href="./size.html" class="identifier">size</a>
  23 {
  24     typedef <em>unspecified</em> type;
  25 };
  26 </pre>
  27 </div>
  28 <div class="section" id="id363">
  29 <h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
  30 <p><tt class="literal"><span class="pre"><a href="./size.html" class="identifier">size</a></span></tt> returns the number of elements in the sequence, that is, the number of elements
  31 in the range [<tt class="literal"><span class="pre"><a href="./begin.html" class="identifier">begin</a>&lt;Sequence&gt;::type</span></tt>, <tt class="literal"><span class="pre"><a href="./end.html" class="identifier">end</a>&lt;Sequence&gt;::type</span></tt>).</p>
  32 </div>
  33 <div class="section" id="id364">
  34 <h3><a class="subsection-title" href="#header" name="header">Header</a></h3>
  35 <pre class="literal-block">
  36 #include &lt;<a href="../../../../boost/mpl/size.hpp" class="header">boost/mpl/size.hpp</a>&gt;
  37 </pre>
  38 </div>
  39 <div class="section" id="id365">
  40 <h3><a class="subsection-title" href="#model-of" name="model-of">Model of</a></h3>
  41 <p><a class="reference internal" href="./tag-dispatched-metafunction.html">Tag Dispatched Metafunction</a></p>
  42 </div>
  43 <div class="section" id="id366">
  44 <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3>
  45 <table border="1" class="docutils table">
  46 <colgroup>
  47 <col width="18%" />
  48 <col width="27%" />
  49 <col width="55%" />
  50 </colgroup>
  51 <thead valign="bottom">
  52 <tr><th class="head">Parameter</th>
  53 <th class="head">Requirement</th>
  54 <th class="head">Description</th>
  55 </tr>
  56 </thead>
  57 <tbody valign="top">
  58 <tr><td><tt class="literal"><span class="pre">Sequence</span></tt></td>
  59 <td><a class="reference internal" href="./forward-sequence.html">Forward Sequence</a></td>
  60 <td>A sequence to query.</td>
  61 </tr>
  62 </tbody>
  63 </table>
  64 </div>
  65 <div class="section" id="id367">
  66 <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
  67 <p>For any <a class="reference internal" href="./forward-sequence.html">Forward Sequence</a> <tt class="literal"><span class="pre">s</span></tt>:</p>
  68 <pre class="literal-block">
  69 typedef <a href="./size.html" class="identifier">size</a>&lt;s&gt;::type n;
  70 </pre>
  71 <table class="docutils field-list" frame="void" rules="none">
  72 <col class="field-name" />
  73 <col class="field-body" />
  74 <tbody valign="top">
  75 <tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first"><a class="reference internal" href="./integral-constant.html">Integral Constant</a>.</p>
  76 </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="literal-block">
  80 typedef <a href="./distance.html" class="identifier">distance</a>&lt; <a href="./begin.html" class="identifier">begin</a>&lt;s&gt;::type,<a href="./end.html" class="identifier">end</a>&lt;s&gt;::type &gt;::type n;
  81 </pre>
  82 </td>
  83 </tr>
  84 <tr class="field"><th class="field-name">Postcondition:</th><td class="field-body"><p class="first last"><tt class="literal"><span class="pre">n::value</span> <span class="pre">&gt;=</span> <span class="pre">0</span></tt>.</p>
  85 </td>
  86 </tr>
  87 </tbody>
  88 </table>
  89 </div>
  90 <div class="section" id="id368">
  91 <h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3>
  92 <p>The complexity of the <tt class="literal"><span class="pre"><a href="./size.html" class="identifier">size</a></span></tt> metafunction directly depends on the implementation of
  93 the particular sequence it is applied to. In the worst case, <tt class="literal"><span class="pre"><a href="./size.html" class="identifier">size</a></span></tt> guarantees a
  94 linear complexity.</p>
  95 <p>If the <tt class="literal"><span class="pre">s</span></tt> is a <a class="reference internal" href="./random-access-sequence.html">Random Access Sequence</a>, <tt class="literal"><span class="pre"><a href="./size.html" class="identifier">size</a>&lt;s&gt;::type</span></tt> is an <em>O(1)</em> operation.
  96 The opposite is not necessarily true — for example, a sequence class that models
  97 <a class="reference internal" href="./forward-sequence.html">Forward Sequence</a> might still give us an <em>O(1)</em> <tt class="literal"><span class="pre"><a href="./size.html" class="identifier">size</a></span></tt> implementation.</p>
  98 </div>
  99 <div class="section" id="id369">
 100 <h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
 101 <pre class="literal-block">
 102 typedef list0&lt;&gt; empty_list;
 103 typedef <a href="./vector-c.html" class="identifier">vector_c</a>&lt;int,0,1,2,3,4,5&gt; numbers;
 104 typedef <a href="./range-c.html" class="identifier">range_c</a>&lt;int,0,100&gt; more_numbers;
 105
 106 <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( <a href="./size.html" class="identifier">size</a>&lt;<a href="./list.html" class="identifier">list</a>&gt;::value, ==, 0 );
 107 <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( <a href="./size.html" class="identifier">size</a>&lt;numbers&gt;::value, ==, 5 );
 108 <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( <a href="./size.html" class="identifier">size</a>&lt;more_numbers&gt;::value, ==, 100 );
 109 </pre>
 110 </div>
 111 <div class="section" id="id370">
 112 <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
 113 <p><a class="reference internal" href="./forward-sequence.html">Forward Sequence</a>, <a class="reference internal" href="./random-access-sequence.html">Random Access Sequence</a>, <a class="reference internal" href="./empty.html">empty</a>, <a class="reference internal" href="./begin.html">begin</a>, <a class="reference internal" href="./end.html">end</a>, <a class="reference internal" href="./distance.html">distance</a></p>
 114 <!-- Sequences/Intrinsic Metafunctions//value_type -->
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