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| <div class="section" id="iterator-category"> |
| <h1><a class="toc-backref" href="./iterator-metafunctions.html#id1459">iterator_category</a></h1> |
| <div class="section" id="id445"> |
| <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> |
| <pre class="literal-block"> |
| template< |
| typename Iterator |
| > |
| struct <a href="./iterator-category.html" class="identifier">iterator_category</a> |
| { |
| typedef typename Iterator::category type; |
| }; |
| </pre> |
| </div> |
| <div class="section" id="id446"> |
| <h3><a class="subsection-title" href="#description" name="description">Description</a></h3> |
| <p>Returns one of the following iterator category tags:</p> |
| <ul class="simple"> |
| <li><tt class="literal"><span class="pre">forward_iterator_tag</span></tt></li> |
| <li><tt class="literal"><span class="pre">bidirectional_iterator_tag</span></tt></li> |
| <li><tt class="literal"><span class="pre">random_access_iterator_tag</span></tt></li> |
| </ul> |
| </div> |
| <div class="section" id="id447"> |
| <h3><a class="subsection-title" href="#header" name="header">Header</a></h3> |
| <pre class="literal-block"> |
| #include <<a href="../../../../boost/mpl/iterator_category.hpp" class="header">boost/mpl/iterator_category.hpp</a>> |
| #include <<a href="../../../../boost/mpl/iterator_tags.hpp" class="header">boost/mpl/iterator_tags.hpp</a>> |
| </pre> |
| </div> |
| <div class="section" id="id448"> |
| <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> |
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| <col width="28%" /> |
| <col width="53%" /> |
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| <thead valign="bottom"> |
| <tr><th class="head">Parameter</th> |
| <th class="head">Requirement</th> |
| <th class="head">Description</th> |
| </tr> |
| </thead> |
| <tbody valign="top"> |
| <tr><td><tt class="literal"><span class="pre">Iterator</span></tt></td> |
| <td><a class="reference internal" href="./forward-iterator.html">Forward Iterator</a></td> |
| <td>The iterator to obtain a category for.</td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="section" id="id449"> |
| <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> |
| <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> |
| <pre class="literal-block"> |
| typedef <a href="./iterator-category.html" class="identifier">iterator_category</a><iter>::type tag; |
| </pre> |
| <table class="docutils field-list" frame="void" rules="none"> |
| <col class="field-name" /> |
| <col class="field-body" /> |
| <tbody valign="top"> |
| <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> |
| </td> |
| </tr> |
| <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>, |
| <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>, |
| 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> |
| </td> |
| </tr> |
| <tr class="field"><th class="field-name">Postcondition:</th><td class="field-body"><dl class="first last docutils"> |
| <dt><tt class="literal"><span class="pre">forward_iterator_tag::value</span> <span class="pre"><</span> <span class="pre">bidirectional_iterator_tag::value</span></tt>,</dt> |
| <dd><p class="first last"><tt class="literal"><span class="pre">bidirectional_iterator_tag::value</span> <span class="pre"><</span> <span class="pre">random_access_iterator_tag::value</span></tt>.</p> |
| </dd> |
| </dl> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="section" id="id450"> |
| <h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3> |
| <p>Amortized constant time.</p> |
| </div> |
| <div class="section" id="id451"> |
| <h3><a class="subsection-title" href="#example" name="example">Example</a></h3> |
| <pre class="literal-block"> |
| template< typename Tag, typename Iterator > |
| struct algorithm_impl |
| { |
| // <em>O(n)</em> implementation |
| }; |
| |
| template< typename Iterator > |
| struct algorithm_impl<random_access_iterator_tag,Iterator> |
| { |
| // <em>O(1)</em> implementation |
| }; |
| |
| template< typename Iterator > |
| struct algorithm |
| : algorithm_impl< |
| <a href="./iterator-category.html" class="identifier">iterator_category</a><Iterator>::type |
| , Iterator |
| > |
| { |
| }; |
| </pre> |
| </div> |
| <div class="section" id="id452"> |
| <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> |
| <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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