86 lines
6.9 KiB
HTML
86 lines
6.9 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: Trivial Metafunction</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="./numeric-metafunction.html" class="navigation-link">Prev</a> <a href="./type-selection.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./numeric-metafunction.html" class="navigation-link">Back</a> Along</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>
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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="./metafunctions-concepts.html" class="navigation-link">Concepts</a> / <a href="./trivial-metafunction.html" class="navigation-link">Trivial Metafunction</a></td>
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</tr></table><div class="header-separator"></div>
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<div class="section" id="trivial-metafunction">
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<h1><a class="toc-backref" href="./metafunctions-concepts.html#id1518">Trivial Metafunction</a></h1>
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<div class="section" id="id853">
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<h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
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<p>A <a class="reference internal" href="./trivial-metafunction.html">Trivial Metafunction</a> accepts a single argument of a class type <tt class="literal"><span class="pre">x</span></tt> and
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returns the <tt class="literal"><span class="pre">x</span></tt>'s nested type member <tt class="literal"><span class="pre">x::name</span></tt>, where <tt class="literal"><span class="pre">name</span></tt> is
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a placeholder token for the actual member's name accessed by a specific
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metafunction's instance. By convention, all <a class="reference internal" href="./trivial-metafunctions-summary.html">trivial metafunctions</a> in MPL
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are named after the members they provide assess to. For instance, a <a class="reference internal" href="./trivial-metafunction.html">Trivial Metafunction</a> named <tt class="literal"><span class="pre">first</span></tt> reaches for the <tt class="literal"><span class="pre">x</span></tt>'s nested member
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<tt class="literal"><span class="pre">::first</span></tt>.</p>
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</div>
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<div class="section" id="id855">
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<h3><a class="subsection-title" href="#expression-requirements" name="expression-requirements">Expression requirements</a></h3>
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<p>In the following table and subsequent specifications, <tt class="literal"><span class="pre">name</span></tt> is placeholder token for the names of
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the <a class="reference internal" href="./trivial-metafunction.html">Trivial Metafunction</a> itself and the accessed member, and <tt class="literal"><span class="pre">x</span></tt> is
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a class type such that <tt class="literal"><span class="pre">x::name</span></tt> is a valid <em>type-name</em>.</p>
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<table border="1" class="docutils table">
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<colgroup>
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<col width="37%" />
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<col width="26%" />
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<col width="37%" />
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</colgroup>
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<thead valign="bottom">
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<tr><th class="head">Expression</th>
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<th class="head">Type</th>
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<th class="head">Complexity</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">name<x>::type</span></tt></td>
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<td>Any type</td>
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<td>Constant time.</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="id856">
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<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
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<pre class="literal-block">
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typedef name<x>::type r;
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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">Precondition:</th><td class="field-body"><tt class="literal"><span class="pre">x::name</span></tt> is a valid <em>type-name</em>.</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">is_same<r,x::name>::value</span> <span class="pre">==</span> <span class="pre">true</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="id857">
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<h3><a class="subsection-title" href="#models" name="models">Models</a></h3>
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<ul class="simple">
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<li><a class="reference internal" href="./trivial-metafunctions-summary.html#first">first</a></li>
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<li><a class="reference internal" href="./trivial-metafunctions-summary.html#second">second</a></li>
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<li><a class="reference internal" href="./trivial-metafunctions-summary.html#base">base</a></li>
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</ul>
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</div>
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<div class="section" id="id858">
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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="./metafunctions.html">Metafunctions</a>, <a class="reference internal" href="./trivial.html#label-metafunctions-trivial">Trivial Metafunctions</a>, <a class="reference internal" href="./identity.html">identity</a></p>
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</div>
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</div>
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<div class="footer-separator"></div>
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<table class="footer"><tr class="footer"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./numeric-metafunction.html" class="navigation-link">Prev</a> <a href="./type-selection.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./numeric-metafunction.html" class="navigation-link">Back</a> Along</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>
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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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</html>
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