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

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  14 <div class="section" id="bidirectional-iterator">
  15 <h1><a class="toc-backref" href="./iterators-concepts.html#id1451">Bidirectional Iterator</a></h1>
  16 <div class="section" id="id390">
  17 <h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
  18 <p>A <a class="reference internal" href="./bidirectional-iterator.html">Bidirectional Iterator</a> is a <a class="reference internal" href="./forward-iterator.html">Forward Iterator</a> that provides a way to
  19 obtain an iterator to the previous element in a sequence.</p>
  20 </div>
  21 <div class="section" id="id391">
  22 <h3><a class="subsection-title" href="#refinement-of" name="refinement-of">Refinement of</a></h3>
  23 <p><a class="reference internal" href="./forward-iterator.html">Forward Iterator</a></p>
  24 </div>
  25 <div class="section" id="id392">
  26 <h3><a class="subsection-title" href="#definitions" name="definitions">Definitions</a></h3>
  27 <ul class="simple">
  28 <li>a bidirectional iterator <tt class="literal"><span class="pre">i</span></tt> is <cite>decrementable</cite> if there is a &quot;previous&quot;
  29 iterator, that is, if <tt class="literal"><span class="pre"><a href="./prior.html" class="identifier">prior</a>&lt;i&gt;::type</span></tt> expression is well-defined;
  30 iterators pointing to the first element of the sequence are not
  31 decrementable.</li>
  32 </ul>
  33 </div>
  34 <div class="section" id="id393">
  35 <h3><a class="subsection-title" href="#expression-requirements" name="expression-requirements">Expression requirements</a></h3>
  36 <p>In addition to the requirements defined in <a class="reference internal" href="./forward-iterator.html">Forward Iterator</a>,
  37 the following requirements must be met.</p>
  38 <table border="1" class="docutils table">
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  40 <col width="25%" />
  41 <col width="46%" />
  42 <col width="29%" />
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  44 <thead valign="bottom">
  45 <tr><th class="head">Expression</th>
  46 <th class="head">Type</th>
  47 <th class="head">Complexity</th>
  48 </tr>
  49 </thead>
  50 <tbody valign="top">
  51 <tr><td><tt class="literal"><span class="pre"><a href="./next.html" class="identifier">next</a>&lt;i&gt;::type</span></tt></td>
  52 <td><a class="reference internal" href="./bidirectional-iterator.html">Bidirectional Iterator</a></td>
  53 <td>Amortized constant time</td>
  54 </tr>
  55 <tr><td><tt class="literal"><span class="pre"><a href="./prior.html" class="identifier">prior</a>&lt;i&gt;::type</span></tt></td>
  56 <td><a class="reference internal" href="./bidirectional-iterator.html">Bidirectional Iterator</a></td>
  57 <td>Amortized constant time</td>
  58 </tr>
  59 <tr><td><tt class="literal"><span class="pre">i::category</span></tt></td>
  60 <td><a class="reference internal" href="./integral-constant.html">Integral Constant</a>, convertible
  61 to <tt class="literal"><span class="pre">bidirectional_iterator_tag</span></tt></td>
  62 <td>Constant time</td>
  63 </tr>
  64 </tbody>
  65 </table>
  66 </div>
  67 <div class="section" id="id394">
  68 <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
  69 <pre class="literal-block">
  70 typedef <a href="./prior.html" class="identifier">prior</a>&lt;i&gt;::type j;
  71 </pre>
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  76 <tr class="field"><th class="field-name">Precondition:</th><td class="field-body"><tt class="literal"><span class="pre">i</span></tt> is decrementable</td>
  77 </tr>
  78 <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><tt class="literal"><span class="pre">j</span></tt> is an iterator pointing to the previous element of the
  79 sequence</td>
  80 </tr>
  81 <tr class="field"><th class="field-name">Postcondition:</th><td class="field-body"><tt class="literal"><span class="pre">j</span></tt> is dereferenceable and incrementable</td>
  82 </tr>
  83 </tbody>
  84 </table>
  85 </div>
  86 <div class="section" id="id395">
  87 <h3><a class="subsection-title" href="#invariants" name="invariants">Invariants</a></h3>
  88 <p>For any bidirectional iterators <tt class="literal"><span class="pre">i</span></tt> and <tt class="literal"><span class="pre">j</span></tt> the following invariants
  89 always hold:</p>
  90 <ul class="simple">
  91 <li>If <tt class="literal"><span class="pre">i</span></tt> is incrementable, then <tt class="literal"><span class="pre"><a href="./prior.html" class="identifier">prior</a>&lt;</span> <span class="pre"><a href="./next.html" class="identifier">next</a>&lt;i&gt;::type</span> <span class="pre">&gt;::type</span></tt> is a null
  92 operation; similarly, if <tt class="literal"><span class="pre">i</span></tt> is decrementable, <tt class="literal"><span class="pre"><a href="./next.html" class="identifier">next</a>&lt;</span> <span class="pre"><a href="./prior.html" class="identifier">prior</a>&lt;i&gt;::type</span> <span class="pre">&gt;::type</span></tt>
  93 is a null operation.</li>
  94 </ul>
  95 </div>
  96 <div class="section" id="id396">
  97 <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
  98 <p><a class="reference internal" href="./iterators.html">Iterators</a>, <a class="reference internal" href="./forward-iterator.html">Forward Iterator</a>, <a class="reference internal" href="./random-access-iterator.html">Random Access Iterator</a>, <a class="reference internal" href="./bidirectional-sequence.html">Bidirectional Sequence</a>, <a class="reference internal" href="./prior.html">prior</a></p>
  99 <!-- Iterators/Concepts//Random Access Iterator |30 -->
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