ceph/src/boost/libs/mpl/doc/refmanual/iterator-category.html

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  14 <div class="section" id="iterator-category">
  15 <h1><a class="toc-backref" href="./iterator-metafunctions.html#id1459">iterator_category</a></h1>
  16 <div class="section" id="id445">
  17 <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
  18 <pre class="literal-block">
  19 template&lt;
  20       typename Iterator
  21     &gt;
  22 struct <a href="./iterator-category.html" class="identifier">iterator_category</a>
  23 {
  24     typedef typename Iterator::category type;
  25 };
  26 </pre>
  27 </div>
  28 <div class="section" id="id446">
  29 <h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
  30 <p>Returns one of the following iterator category tags:</p>
  31 <ul class="simple">
  32 <li><tt class="literal"><span class="pre">forward_iterator_tag</span></tt></li>
  33 <li><tt class="literal"><span class="pre">bidirectional_iterator_tag</span></tt></li>
  34 <li><tt class="literal"><span class="pre">random_access_iterator_tag</span></tt></li>
  35 </ul>
  36 </div>
  37 <div class="section" id="id447">
  38 <h3><a class="subsection-title" href="#header" name="header">Header</a></h3>
  39 <pre class="literal-block">
  40 #include &lt;<a href="../../../../boost/mpl/iterator_category.hpp" class="header">boost/mpl/iterator_category.hpp</a>&gt;
  41 #include &lt;<a href="../../../../boost/mpl/iterator_tags.hpp" class="header">boost/mpl/iterator_tags.hpp</a>&gt;
  42 </pre>
  43 </div>
  44 <div class="section" id="id448">
  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="19%" />
  49 <col width="28%" />
  50 <col width="53%" />
  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">Iterator</span></tt></td>
  60 <td><a class="reference internal" href="./forward-iterator.html">Forward Iterator</a></td>
  61 <td>The iterator to obtain a category for.</td>
  62 </tr>
  63 </tbody>
  64 </table>
  65 </div>
  66 <div class="section" id="id449">
  67 <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
  68 <p>For any <a class="reference internal" href="./forward-iterator.html">Forward Iterator</a>s <tt class="literal"><span class="pre">iter</span></tt>:</p>
  69 <pre class="literal-block">
  70 typedef <a href="./iterator-category.html" class="identifier">iterator_category</a>&lt;iter&gt;::type tag;
  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="./integral-constant.html">Integral Constant</a>.</p>
  77 </td>
  78 </tr>
  79 <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first"><tt class="literal"><span class="pre">tag</span></tt> is <tt class="literal"><span class="pre">forward_iterator_tag</span></tt> if <tt class="literal"><span class="pre">iter</span></tt> is a model of <a class="reference internal" href="./forward-iterator.html">Forward Iterator</a>,
  80 <tt class="literal"><span class="pre">bidirectional_iterator_tag</span></tt> if <tt class="literal"><span class="pre">iter</span></tt> is a model of <a class="reference internal" href="./bidirectional-iterator.html">Bidirectional Iterator</a>,
  81 or <tt class="literal"><span class="pre">random_access_iterator_tag</span></tt> if <tt class="literal"><span class="pre">iter</span></tt> is a model of <a class="reference internal" href="./random-access-iterator.html">Random Access Iterator</a>;</p>
  82 </td>
  83 </tr>
  84 <tr class="field"><th class="field-name">Postcondition:</th><td class="field-body"><dl class="first last docutils">
  85 <dt><tt class="literal"><span class="pre">forward_iterator_tag::value</span> <span class="pre">&lt;</span> <span class="pre">bidirectional_iterator_tag::value</span></tt>,</dt>
  86 <dd><p class="first last"><tt class="literal"><span class="pre">bidirectional_iterator_tag::value</span> <span class="pre">&lt;</span> <span class="pre">random_access_iterator_tag::value</span></tt>.</p>
  87 </dd>
  88 </dl>
  89 </td>
  90 </tr>
  91 </tbody>
  92 </table>
  93 </div>
  94 <div class="section" id="id450">
  95 <h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3>
  96 <p>Amortized constant time.</p>
  97 </div>
  98 <div class="section" id="id451">
  99 <h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
 100 <pre class="literal-block">
 101 template&lt; typename Tag, typename Iterator &gt;
 102 struct algorithm_impl
 103 {
 104     // <em>O(n)</em> implementation
 105 };
 106
 107 template&lt; typename Iterator &gt;
 108 struct algorithm_impl&lt;random_access_iterator_tag,Iterator&gt;
 109 {
 110     // <em>O(1)</em> implementation
 111 };
 112
 113 template&lt; typename Iterator &gt;
 114 struct algorithm
 115     : algorithm_impl&lt;
 116           <a href="./iterator-category.html" class="identifier">iterator_category</a>&lt;Iterator&gt;::type
 117         , Iterator
 118         >
 119 {
 120 };
 121 </pre>
 122 </div>
 123 <div class="section" id="id452">
 124 <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
 125 <p><a class="reference internal" href="./iterators.html">Iterators</a>, <a class="reference internal" href="./begin.html">begin</a> / <a class="reference internal" href="./end.html">end</a>, <a class="reference internal" href="./advance.html">advance</a>, <a class="reference internal" href="./distance.html">distance</a>, <a class="reference internal" href="./next.html">next</a></p>
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