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| <title>The MPL Reference Manual: Metafunction Class</title> |
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| <table class="header"><tr class="header"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./metafunction.html" class="navigation-link">Prev</a> <a href="./lambda-expression.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./metafunction.html" class="navigation-link">Back</a> <a href="./lambda-expression.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./metafunctions-concepts.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> |
| <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="./metafunctions-concepts.html" class="navigation-link">Concepts</a> / <a href="./metafunction-class.html" class="navigation-link">Metafunction Class</a></td> |
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| <div class="section" id="metafunction-class"> |
| <h1><a class="toc-backref" href="./metafunctions-concepts.html#id1513">Metafunction Class</a></h1> |
| <div class="section" id="summary"> |
| <h3>Summary</h3> |
| <p>A <em>metafunction class</em> is a certain form of metafunction representation |
| that enables higher-order metaprogramming. More precisely, it's a class |
| with a publicly-accessible nested <a class="reference internal" href="./metafunction.html">Metafunction</a> called <tt class="literal"><span class="pre"><a href="./apply.html" class="identifier">apply</a></span></tt>. |
| Correspondingly, a metafunction class invocation is defined as invocation |
| of its nested <tt class="literal"><span class="pre"><a href="./apply.html" class="identifier">apply</a></span></tt> metafunction.</p> |
| </div> |
| <div class="section" id="id827"> |
| <h3><a class="subsection-title" href="#expression-requirements" name="expression-requirements">Expression requirements</a></h3> |
| <p>In the following table and subsequent specifications, <tt class="literal"><span class="pre">f</span></tt> is a <a class="reference internal" href="./metafunction-class.html">Metafunction Class</a>.</p> |
| <table border="1" class="docutils table"> |
| <colgroup> |
| <col width="36%" /> |
| <col width="32%" /> |
| <col width="32%" /> |
| </colgroup> |
| <thead valign="bottom"> |
| <tr><th class="head">Expression</th> |
| <th class="head">Type</th> |
| <th class="head">Complexity</th> |
| </tr> |
| </thead> |
| <tbody valign="top"> |
| <tr><td><tt class="literal"><span class="pre">f::<a href="./apply.html" class="identifier">apply</a>::type</span></tt></td> |
| <td>Any type</td> |
| <td>Unspecified.</td> |
| </tr> |
| <tr><td><tt class="literal"><span class="pre">f::<a href="./apply.html" class="identifier">apply</a><>::type</span></tt></td> |
| <td>Any type</td> |
| <td>Unspecified.</td> |
| </tr> |
| <tr><td><tt class="literal"><span class="pre">f::<a href="./apply.html" class="identifier">apply</a><a1,...an>::type</span></tt></td> |
| <td>Any type</td> |
| <td>Unspecified.</td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="section" id="id828"> |
| <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> |
| <pre class="literal-block"> |
| typedef f::<a href="./apply.html" class="identifier">apply</a>::type x; |
| </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">Precondition:</th><td class="field-body"><tt class="literal"><span class="pre">f</span></tt> is a nullary <a class="reference internal" href="./metafunction-class.html">Metafunction Class</a>; <tt class="literal"><span class="pre">f::<a href="./apply.html" class="identifier">apply</a>::type</span></tt> is a <em>type-name</em>.</td> |
| </tr> |
| <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><tt class="literal"><span class="pre">x</span></tt> is the result of the metafunction class invocation.</td> |
| </tr> |
| </tbody> |
| </table> |
| <!-- ................................................................................... --> |
| <pre class="literal-block"> |
| typedef f::<a href="./apply.html" class="identifier">apply</a><>::type x; |
| </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">Precondition:</th><td class="field-body"><tt class="literal"><span class="pre">f</span></tt> is a nullary <a class="reference internal" href="./metafunction-class.html">Metafunction Class</a>; <tt class="literal"><span class="pre">f::<a href="./apply.html" class="identifier">apply</a><>::type</span></tt> is a <em>type-name</em>.</td> |
| </tr> |
| <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><tt class="literal"><span class="pre">x</span></tt> is the result of the metafunction class invocation.</td> |
| </tr> |
| </tbody> |
| </table> |
| <!-- ................................................................................... --> |
| <pre class="literal-block"> |
| typedef f::<a href="./apply.html" class="identifier">apply</a><a1,<em>...</em>a<em>n</em>>::type x; |
| </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">Precondition:</th><td class="field-body"><tt class="literal"><span class="pre">f</span></tt> is an <em>n</em>-ary metafunction class; <tt class="literal"><span class="pre"><a href="./apply.html" class="identifier">apply</a></span></tt> is a <a class="reference internal" href="./metafunction.html">Metafunction</a>.</td> |
| </tr> |
| <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><tt class="literal"><span class="pre">x</span></tt> is the result of the metafunction class |
| invocation with the actual arguments <tt class="literal"><span class="pre">a1</span></tt>,... <tt class="literal"><span class="pre">an</span></tt>.</td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="section" id="id829"> |
| <h3><a class="subsection-title" href="#models" name="models">Models</a></h3> |
| <ul class="simple"> |
| <li><a class="reference internal" href="./always.html">always</a></li> |
| <li><a class="reference internal" href="./arg.html">arg</a></li> |
| <li><a class="reference internal" href="./quote.html">quote</a></li> |
| <li><a class="reference internal" href="./numeric-cast.html">numeric_cast</a></li> |
| <li><a class="reference internal" href="./unpack-args.html">unpack_args</a></li> |
| </ul> |
| </div> |
| <div class="section" id="id830"> |
| <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="./metafunction.html">Metafunction</a>, <a class="reference internal" href="./lambda-expression.html">Lambda Expression</a>, <a class="reference internal" href="./invocation.html">invocation</a>, <a class="reference internal" href="./apply-wrap.html">apply_wrap</a>, <a class="reference internal" href="./bind.html">bind</a>, <a class="reference internal" href="./quote.html">quote</a></p> |
| <!-- Metafunctions/Concepts//Lambda Expression |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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