124 lines
9.1 KiB
HTML
124 lines
9.1 KiB
HTML
<?xml version="1.0" encoding="utf-8" ?>
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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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<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<meta name="generator" content="Docutils 0.7: http://docutils.sourceforge.net/" />
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<title>The MPL Reference Manual: size</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="./sequence-tag.html" class="navigation-link">Prev</a> <a href="./value-type.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./sequence-tag.html" class="navigation-link">Back</a> <a href="./value-type.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./intrinsic-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="./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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</tr></table><div class="header-separator"></div>
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<div class="section" id="size">
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<h1><a class="toc-backref" href="./intrinsic-metafunctions.html#id1446">size</a></h1>
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<div class="section" id="id362">
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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 Sequence
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>
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struct <a href="./size.html" class="identifier">size</a>
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{
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typedef <em>unspecified</em> type;
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};
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</pre>
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</div>
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<div class="section" id="id363">
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<h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
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<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
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in the range [<tt class="literal"><span class="pre"><a href="./begin.html" class="identifier">begin</a><Sequence>::type</span></tt>, <tt class="literal"><span class="pre"><a href="./end.html" class="identifier">end</a><Sequence>::type</span></tt>).</p>
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</div>
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<div class="section" id="id364">
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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/size.hpp" class="header">boost/mpl/size.hpp</a>>
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</pre>
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</div>
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<div class="section" id="id365">
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<h3><a class="subsection-title" href="#model-of" name="model-of">Model of</a></h3>
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<p><a class="reference internal" href="./tag-dispatched-metafunction.html">Tag Dispatched Metafunction</a></p>
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</div>
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<div class="section" id="id366">
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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="18%" />
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<col width="27%" />
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<col width="55%" />
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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">Sequence</span></tt></td>
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<td><a class="reference internal" href="./forward-sequence.html">Forward Sequence</a></td>
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<td>A sequence to query.</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="id367">
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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-sequence.html">Forward Sequence</a> <tt class="literal"><span class="pre">s</span></tt>:</p>
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<pre class="literal-block">
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typedef <a href="./size.html" class="identifier">size</a><s>::type n;
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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">Equivalent to</p>
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<pre class="literal-block">
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typedef <a href="./distance.html" class="identifier">distance</a>< <a href="./begin.html" class="identifier">begin</a><s>::type,<a href="./end.html" class="identifier">end</a><s>::type >::type n;
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</pre>
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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"><p class="first last"><tt class="literal"><span class="pre">n::value</span> <span class="pre">>=</span> <span class="pre">0</span></tt>.</p>
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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="id368">
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<h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3>
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<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
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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
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linear complexity.</p>
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<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><s>::type</span></tt> is an <em>O(1)</em> operation.
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The opposite is not necessarily true — for example, a sequence class that models
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<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>
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</div>
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<div class="section" id="id369">
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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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typedef list0<> empty_list;
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typedef <a href="./vector-c.html" class="identifier">vector_c</a><int,0,1,2,3,4,5> numbers;
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typedef <a href="./range-c.html" class="identifier">range_c</a><int,0,100> more_numbers;
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<a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( <a href="./size.html" class="identifier">size</a><<a href="./list.html" class="identifier">list</a>>::value, ==, 0 );
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<a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( <a href="./size.html" class="identifier">size</a><numbers>::value, ==, 5 );
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<a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( <a href="./size.html" class="identifier">size</a><more_numbers>::value, ==, 100 );
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</pre>
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</div>
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<div class="section" id="id370">
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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="./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>
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<!-- Sequences/Intrinsic Metafunctions//value_type -->
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<table class="footer"><tr class="footer"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./sequence-tag.html" class="navigation-link">Prev</a> <a href="./value-type.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./sequence-tag.html" class="navigation-link">Back</a> <a href="./value-type.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./intrinsic-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><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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