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- <title>The MPL Reference Manual: apply_wrap</title>
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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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- <div class="section" id="apply-wrap">
- <h1><a class="toc-backref" href="./invocation.html#id1526">apply_wrap</a></h1>
- <div class="section" id="id894">
- <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
- <pre class="literal-block">
- template<
- typename F
- >
- struct apply_wrap0
- {
- typedef <em>unspecified</em> type;
- };
- template<
- typename F, typename A1
- >
- struct apply_wrap1
- {
- typedef <em>unspecified</em> type;
- };
- <em>...</em>
- template<
- typename F, typename A1,<em>...</em> typename An
- >
- struct <a href="./apply-wrap.html" class="identifier">apply_wrap</a><em>n</em>
- {
- typedef <em>unspecified</em> type;
- };
- </pre>
- </div>
- <div class="section" id="id895">
- <h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
- <p>Invokes a <a class="reference internal" 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>
- <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
- <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).
- They provide a more concise notation and higher portability than their
- underlaying constructs at the cost of an extra template instantiation.</p>
- </div>
- <div class="section" id="id896">
- <h3><a class="subsection-title" href="#header" name="header">Header</a></h3>
- <pre class="literal-block">
- #include <<a href="../../../../boost/mpl/apply_wrap.hpp" class="header">boost/mpl/apply_wrap.hpp</a>>
- </pre>
- </div>
- <div class="section" id="id897">
- <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3>
- <table border="1" class="docutils table">
- <colgroup>
- <col width="15%" />
- <col width="36%" />
- <col width="48%" />
- </colgroup>
- <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">F</span></tt></td>
- <td><a class="reference internal" href="./metafunction-class.html">Metafunction Class</a></td>
- <td>A metafunction class to invoke.</td>
- </tr>
- <tr><td><tt class="literal"><span class="pre">A1</span></tt>,... <tt class="literal"><span class="pre">An</span></tt></td>
- <td>Any type</td>
- <td>Invocation arguments.</td>
- </tr>
- </tbody>
- </table>
- </div>
- <div class="section" id="id898">
- <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
- <p>For any <a class="reference internal" 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>
- <pre class="literal-block">
- typedef <a href="./apply-wrap.html" class="identifier">apply_wrap</a><em>n</em><f,a1,<em>...</em>an>::type t;
- </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">Any type.</td>
- </tr>
- <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>,
- 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
- <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
- a class or a class template.</td>
- </tr>
- </tbody>
- </table>
- </div>
- <div class="section" id="id899">
- <h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
- <pre class="literal-block">
- struct f0
- {
- template< typename T = int > struct <a href="./apply.html" class="identifier">apply</a>
- {
- typedef char type;
- };
- };
- struct g0
- {
- struct <a href="./apply.html" class="identifier">apply</a> { typedef char type; };
- };
- struct f2
- {
- template< typename T1, typename T2 > struct <a href="./apply.html" class="identifier">apply</a>
- {
- typedef T2 type;
- };
- };
- typedef <a href="./apply-wrap.html" class="identifier">apply_wrap</a><tt class="literal"><span class="pre">0</span></tt>< f0 >::type r1;
- typedef <a href="./apply-wrap.html" class="identifier">apply_wrap</a><tt class="literal"><span class="pre">0</span></tt>< g0 >::type r2;
- 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;
- <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same<r1,char> ));
- <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same<r2,char> ));
- <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same<r3,char> ));
- </pre>
- </div>
- <div class="section" id="id900">
- <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
- <p><a class="reference internal" href="./metafunctions.html">Metafunctions</a>, <a class="reference internal" href="./invocation.html">invocation</a>, <a class="reference internal" href="./apply.html">apply</a>, <a class="reference internal" href="./lambda.html">lambda</a>, <a class="reference internal" href="./quote.html">quote</a>, <a class="reference internal" href="./bind.html">bind</a>, <a class="reference internal" href="./protect.html">protect</a></p>
- <!-- Metafunctions/Invocation//unpack_args |30 -->
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- <td><div class="copyright-footer"><div class="copyright">Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams</div>
- Distributed under the Boost Software License, Version 1.0. (See accompanying
- 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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