boost_mpl/doc/refmanual/metafunction-class.html

<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<!-- Copyright Aleksey Gurtovoy 2006. Distributed under the Boost -->
<!-- Software License, Version 1.0. (See accompanying -->
<!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="generator" content="Docutils 0.3.6: http://docutils.sourceforge.net/" />
<title>The MPL Reference Manual: Metafunction Class</title>
<link rel="stylesheet" href="../style.css" type="text/css" />
</head>
<body class="docframe refmanual">
<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>&nbsp;<a href="./lambda-expression.html" class="navigation-link">Next</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./metafunction.html" class="navigation-link">Back</a>&nbsp;<a href="./lambda-expression.html" class="navigation-link">Along</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./metafunctions-concepts.html" class="navigation-link">Up</a>&nbsp;<a href="../refmanual.html" class="navigation-link">Home</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</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>
</tr></table><div class="header-separator"></div>
<div class="section" id="metafunction-class">
<h1><a class="toc-backref" href="./metafunctions-concepts.html#id439" name="metafunction-class">Metafunction Class</a></h1>
<div class="section" id="summary">
<h3><a class="subsection-title" href="#summary" name="summary">Summary</a></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" 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="metafunctions-metafunction-expression-requirements">
<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" href="./metafunction-class.html">Metafunction Class</a>.</p>
<table border="1" class="table">
<colgroup>
<col width="36%" />
<col width="32%" />
<col width="32%" />
</colgroup>
<thead valign="bottom">
<tr><th>Expression</th>
<th>Type</th>
<th>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>&lt;&gt;::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>&lt;a1,...an&gt;::type</span></tt></td>
<td>Any type</td>
<td>Unspecified.</td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="metafunctions-metafunction-expression-semantics">
<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="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" 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>&lt;&gt;::type x;
</pre>
<table class="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" href="./metafunction-class.html">Metafunction Class</a>; <tt class="literal"><span class="pre">f::<a href="./apply.html" class="identifier">apply</a>&lt;&gt;::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>&lt;a1,<em>...</em>a<em>n</em>&gt;::type x;
</pre>
<table class="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" 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="metafunctions-metafunction-models">
<h3><a class="subsection-title" href="#models" name="models">Models</a></h3>
<ul class="simple">
<li><a class="refentry reference" href="./always.html"><tt class="refentry literal"><span class="pre">always</span></tt></a></li>
<li><a class="refentry reference" href="./arg.html"><tt class="refentry literal"><span class="pre">arg</span></tt></a></li>
<li><a class="refentry reference" href="./quote.html"><tt class="refentry literal"><span class="pre">quote</span></tt></a></li>
<li><a class="refentry reference" href="./numeric-cast.html"><tt class="refentry literal"><span class="pre">numeric_cast</span></tt></a></li>
<li><a class="refentry reference" href="./unpack-args.html"><tt class="refentry literal"><span class="pre">unpack_args</span></tt></a></li>
</ul>
</div>
<div class="section" id="metafunctions-metafunction-see-also">
<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
<p><a class="reference" href="./metafunctions.html">Metafunctions</a>, <a class="reference" href="./metafunction.html">Metafunction</a>, <a class="reference" href="./lambda-expression.html">Lambda Expression</a>, <a class="reference" href="./invocation.html">invocation</a>, <a class="refentry reference" href="./apply-wrap.html"><tt class="refentry literal"><span class="pre">apply_wrap</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="./quote.html"><tt class="refentry literal"><span class="pre">quote</span></tt></a></p>
<!-- modtime: November 10, 2004 04:37:44 +0000 -->
<!-- Metafunctions/Concepts//Lambda Expression |30 -->
</div>
</div>

<div class="footer-separator"></div>
<table class="footer"><tr class="footer"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./metafunction.html" class="navigation-link">Prev</a>&nbsp;<a href="./lambda-expression.html" class="navigation-link">Next</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./metafunction.html" class="navigation-link">Back</a>&nbsp;<a href="./lambda-expression.html" class="navigation-link">Along</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./metafunctions-concepts.html" class="navigation-link">Up</a>&nbsp;<a href="../refmanual.html" class="navigation-link">Home</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./refmanual_toc.html" class="navigation-link">Full TOC</a></span></td>
</tr></table></body>
</html>