115 lines
7.8 KiB
HTML
115 lines
7.8 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: arg</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="./quote.html" class="navigation-link">Prev</a> <a href="./protect.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./quote.html" class="navigation-link">Back</a> <a href="./protect.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./composition-and-argument-binding.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="./metafunctions.html" class="navigation-link">Metafunctions</a> / <a href="./composition-and-argument-binding.html" class="navigation-link">Composition and Argument Binding</a> / <a href="./arg.html" class="navigation-link">arg</a></td>
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</tr></table><div class="header-separator"></div>
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<div class="section" id="arg">
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<h1><a class="toc-backref" href="./composition-and-argument-binding.html#id1533">arg</a></h1>
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<div class="section" id="id946">
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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< int n > struct <a href="./arg.html" class="identifier">arg</a>;
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template<> struct <a href="./arg.html" class="identifier">arg</a><1>
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{
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template< typename A1,<em>...</em> typename A<em>n</em> = <em>unspecified</em> >
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struct <a href="./apply.html" class="identifier">apply</a>
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{
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typedef A1 type;
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};
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};
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<em>...</em>
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template<> struct <a href="./arg.html" class="identifier">arg</a><<em>n</em>>
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{
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template< typename A1,<em>...</em> typename A<em>n</em> >
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struct <a href="./apply.html" class="identifier">apply</a>
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{
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typedef A<em>n</em> type;
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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="id947">
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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="./arg.html" class="identifier">arg</a><n></span></tt> specialization is a <a class="reference internal" href="./metafunction-class.html">Metafunction Class</a> that return the <tt class="literal"><span class="pre">n</span></tt>th of its arguments.</p>
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</div>
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<div class="section" id="id948">
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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/arg.hpp" class="header">boost/mpl/arg.hpp</a>>
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</pre>
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</div>
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<div class="section" id="id949">
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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="15%" />
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<col width="36%" />
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<col width="48%" />
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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">n</span></tt></td>
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<td>An integral constant</td>
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<td>A number of argument to return.</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="id950">
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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 integral constant <tt class="literal"><span class="pre">n</span></tt> in the range [1, <a class="reference internal" href="./limit-metafunction-arity.html">BOOST_MPL_LIMIT_METAFUNCTION_ARITY</a>] and
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arbitrary types <tt class="literal"><span class="pre">a1</span></tt>,... <tt class="literal"><span class="pre">an</span></tt>:</p>
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<pre class="literal-block">
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typedef <a href="./apply-wrap.html" class="identifier">apply_wrap</a><em>n</em>< <a href="./arg.html" class="identifier">arg</a><<em>n</em>>,a1,<em>...</em>a<em>n</em> >::type x;
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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">A type.</td>
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</tr>
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<tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><tt class="literal"><span class="pre">x</span></tt> is identical to <tt class="literal"><span class="pre">an</span></tt>.</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="id951">
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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 <a href="./apply-wrap.html" class="identifier">apply_wrap</a><tt class="literal"><span class="pre">5</span></tt>< <a href="./arg.html" class="identifier">arg</a><1>,bool,char,short,int,long >::type t1;
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typedef <a href="./apply-wrap.html" class="identifier">apply_wrap</a><tt class="literal"><span class="pre">5</span></tt>< <a href="./arg.html" class="identifier">arg</a><3>,bool,char,short,int,long >::type t3;
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<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same< t1, bool > ));
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<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same< t3, short > ));
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</pre>
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</div>
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<div class="section" id="id952">
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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="./composition-and-argument-binding.html">Composition and Argument Binding</a>, <a class="reference internal" href="./placeholders.html">Placeholders</a>, <a class="reference internal" href="./lambda.html">lambda</a>, <a class="reference internal" href="./bind.html">bind</a>, <a class="reference internal" href="./apply.html">apply</a>, <a class="reference internal" href="./apply-wrap.html">apply_wrap</a></p>
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<!-- Metafunctions/Composition and Argument Binding//protect |60 -->
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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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