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152 lines
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<title>The MPL Reference Manual: apply_wrap</title>
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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="./apply.html" class="navigation-link">Prev</a> <a href="./unpack-args.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./apply.html" class="navigation-link">Back</a> <a href="./unpack-args.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./invocation.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="./invocation.html" class="navigation-link">Invocation</a> / <a href="./apply-wrap.html" class="navigation-link">apply_wrap</a></td>
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</tr></table><div class="header-separator"></div>
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<div class="section" id="apply-wrap">
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<h1><a class="toc-backref" href="./invocation.html#id452" name="apply-wrap">apply_wrap</a></h1>
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<div class="section" id="invocation-apply-synopsis">
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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 F
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>
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struct apply_wrap0
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{
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typedef <em>unspecified</em> type;
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};
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template<
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typename F, typename A1
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>
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struct apply_wrap1
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{
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typedef <em>unspecified</em> type;
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};
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<em>...</em>
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template<
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typename F, typename A1,<em>...</em> typename An
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>
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struct <a href="./apply-wrap.html" class="identifier">apply_wrap</a><em>n</em>
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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="invocation-apply-description">
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<h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
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<p>Invokes a <a class="reference" href="./metafunction-class.html">Metafunction Class</a> <tt class="literal"><span class="pre">F</span></tt> with arguments <tt class="literal"><span class="pre">A1</span></tt>,... <tt class="literal"><span class="pre">An</span></tt>.</p>
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<p>In essence, <tt class="literal"><span class="pre"><a href="./apply-wrap.html" class="identifier">apply_wrap</a></span></tt> forms are nothing more than syntactic wrappers around
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<tt class="literal"><span class="pre">F::<a href="./apply.html" class="identifier">apply</a><A1,...</span> <span class="pre">An>::type</span></tt> / <tt class="literal"><span class="pre">F::<a href="./apply.html" class="identifier">apply</a>::type</span></tt> expressions (hence the name).
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They provide a more concise notation and higher portability than their
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underlaying constructs at the cost of an extra template instantiation.</p>
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</div>
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<div class="section" id="invocation-apply-header">
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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/apply_wrap.hpp" class="header">boost/mpl/apply_wrap.hpp</a>>
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</pre>
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</div>
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<div class="section" id="invocation-apply-parameters">
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<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3>
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<table border="1" class="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>Parameter</th>
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<th>Requirement</th>
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<th>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">F</span></tt></td>
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<td><a class="reference" href="./metafunction-class.html">Metafunction Class</a></td>
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<td>A metafunction class to invoke.</td>
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</tr>
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<tr><td><tt class="literal"><span class="pre">A1</span></tt>,... <tt class="literal"><span class="pre">An</span></tt></td>
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<td>Any type</td>
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<td>Invocation arguments.</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="invocation-apply-expression-semantics">
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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" href="./metafunction-class.html">Metafunction Class</a> <tt class="literal"><span class="pre">f</span></tt> and 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><f,a1,<em>...</em>an>::type t;
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</pre>
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<table class="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">Any type.</td>
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</tr>
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<tr class="field"><th class="field-name">Semantics:</th><td class="field-body">If <tt class="literal"><span class="pre">n</span> <span class="pre">></span> <span class="pre">0</span></tt>, equivalent to <tt class="literal"><span class="pre">typedef</span> <span class="pre">f::<a href="./apply.html" class="identifier">apply</a><a1,...</span> <span class="pre">an>::type</span> <span class="pre">t;</span></tt>,
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otherwise equivalent to either <tt class="literal"><span class="pre">typedef</span> <span class="pre">f::<a href="./apply.html" class="identifier">apply</a>::type</span> <span class="pre">t;</span></tt> or
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<tt class="literal"><span class="pre">typedef</span> <span class="pre">f::<a href="./apply.html" class="identifier">apply</a><>::type</span> <span class="pre">t;</span></tt> depending on whether <tt class="literal"><span class="pre">f::<a href="./apply.html" class="identifier">apply</a></span></tt> is
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a class or a class template.</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="invocation-apply-example">
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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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struct f0
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{
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template< typename T = int > struct <a href="./apply.html" class="identifier">apply</a>
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{
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typedef char type;
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};
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};
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struct g0
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{
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struct <a href="./apply.html" class="identifier">apply</a> { typedef char type; };
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};
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struct f2
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{
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template< typename T1, typename T2 > struct <a href="./apply.html" class="identifier">apply</a>
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{
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typedef T2 type;
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};
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};
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typedef <a href="./apply-wrap.html" class="identifier">apply_wrap</a><tt class="literal"><span class="pre">0</span></tt>< f0 >::type r1;
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typedef <a href="./apply-wrap.html" class="identifier">apply_wrap</a><tt class="literal"><span class="pre">0</span></tt>< g0 >::type r2;
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typedef <a href="./apply-wrap.html" class="identifier">apply_wrap</a><tt class="literal"><span class="pre">2</span></tt>< f2,int,char >::type r3;
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<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same<r1,char> ));
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<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same<r2,char> ));
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<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same<r3,char> ));
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</pre>
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</div>
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<div class="section" id="invocation-apply-see-also">
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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" href="./metafunctions.html">Metafunctions</a>, <a class="reference" href="./invocation.html">invocation</a>, <a class="refentry reference" href="./apply.html"><tt class="refentry literal"><span class="pre">apply</span></tt></a>, <a class="refentry reference" href="./lambda.html"><tt class="refentry literal"><span class="pre">lambda</span></tt></a>, <a class="refentry reference" href="./quote.html"><tt class="refentry literal"><span class="pre">quote</span></tt></a>, <a class="refentry reference" href="./bind.html"><tt class="refentry literal"><span class="pre">bind</span></tt></a>, <a class="refentry reference" href="./protect.html"><tt class="refentry literal"><span class="pre">protect</span></tt></a></p>
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<!-- modtime: November 10, 2004 04:46:09 +0000 -->
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