6f63e9d0c6
[SVN r64705]
135 lines
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135 lines
8.3 KiB
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<meta name="generator" content="Docutils 0.7: http://docutils.sourceforge.net/" />
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<title>The MPL Reference Manual: iterator_category</title>
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<link rel="stylesheet" href="../style.css" type="text/css" />
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</head>
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<body class="docframe refmanual">
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<table class="header"><tr class="header"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./deref.html" class="navigation-link">Prev</a> <a href="./algorithms.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./deref.html" class="navigation-link">Back</a> Along</span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./iterator-metafunctions.html" class="navigation-link">Up</a> <a href="../refmanual.html" class="navigation-link">Home</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./refmanual_toc.html" class="navigation-link">Full TOC</a></span></td>
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<td class="header-group page-location"><a href="../refmanual.html" class="navigation-link">Front Page</a> / <a href="./iterators.html" class="navigation-link">Iterators</a> / <a href="./iterator-metafunctions.html" class="navigation-link">Iterator Metafunctions</a> / <a href="./iterator-category.html" class="navigation-link">iterator_category</a></td>
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</tr></table><div class="header-separator"></div>
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<div class="section" id="iterator-category">
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<h1><a class="toc-backref" href="./iterator-metafunctions.html#id1459">iterator_category</a></h1>
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<div class="section" id="id445">
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<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
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<pre class="literal-block">
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template<
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typename Iterator
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>
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struct <a href="./iterator-category.html" class="identifier">iterator_category</a>
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{
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typedef typename Iterator::category type;
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};
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</pre>
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</div>
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<div class="section" id="id446">
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<h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
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<p>Returns one of the following iterator category tags:</p>
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<ul class="simple">
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<li><tt class="literal"><span class="pre">forward_iterator_tag</span></tt></li>
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<li><tt class="literal"><span class="pre">bidirectional_iterator_tag</span></tt></li>
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<li><tt class="literal"><span class="pre">random_access_iterator_tag</span></tt></li>
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</ul>
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</div>
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<div class="section" id="id447">
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<h3><a class="subsection-title" href="#header" name="header">Header</a></h3>
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<pre class="literal-block">
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#include <<a href="../../../../boost/mpl/iterator_category.hpp" class="header">boost/mpl/iterator_category.hpp</a>>
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#include <<a href="../../../../boost/mpl/iterator_tags.hpp" class="header">boost/mpl/iterator_tags.hpp</a>>
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</pre>
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</div>
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<div class="section" id="id448">
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<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3>
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<table border="1" class="docutils table">
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<colgroup>
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<col width="19%" />
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<col width="28%" />
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<col width="53%" />
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</colgroup>
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<thead valign="bottom">
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<tr><th class="head">Parameter</th>
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<th class="head">Requirement</th>
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<th class="head">Description</th>
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</tr>
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</thead>
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<tbody valign="top">
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<tr><td><tt class="literal"><span class="pre">Iterator</span></tt></td>
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<td><a class="reference internal" href="./forward-iterator.html">Forward Iterator</a></td>
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<td>The iterator to obtain a category for.</td>
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</tr>
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</tbody>
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</table>
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</div>
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<div class="section" id="id449">
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<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
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<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>
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<pre class="literal-block">
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typedef <a href="./iterator-category.html" class="identifier">iterator_category</a><iter>::type tag;
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</pre>
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<table class="docutils field-list" frame="void" rules="none">
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<col class="field-name" />
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<col class="field-body" />
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<tbody valign="top">
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<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>
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</td>
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</tr>
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<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>,
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<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>,
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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>
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</td>
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</tr>
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<tr class="field"><th class="field-name">Postcondition:</th><td class="field-body"><dl class="first last docutils">
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<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>
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<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>
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</dd>
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</dl>
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</td>
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</tr>
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</tbody>
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</table>
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</div>
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<div class="section" id="id450">
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<h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3>
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<p>Amortized constant time.</p>
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</div>
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<div class="section" id="id451">
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<h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
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<pre class="literal-block">
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template< typename Tag, typename Iterator >
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struct algorithm_impl
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{
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// <em>O(n)</em> implementation
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};
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template< typename Iterator >
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struct algorithm_impl<random_access_iterator_tag,Iterator>
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{
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// <em>O(1)</em> implementation
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};
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template< typename Iterator >
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struct algorithm
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: algorithm_impl<
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<a href="./iterator-category.html" class="identifier">iterator_category</a><Iterator>::type
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, Iterator
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>
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{
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};
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</pre>
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</div>
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<div class="section" id="id452">
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<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
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<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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<td><div class="copyright-footer"><div class="copyright">Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams</div>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at <a class="reference external" href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)</div></td></tr></table></body>
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