<?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"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <meta name="generator" content="Docutils 0.7: http://docutils.sourceforge.net/" /> <title>The MPL Reference Manual: BOOST_MPL_HAS_XXX_TRAIT_DEF</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="./has-xxx-template-named-def.html" class="navigation-link">Prev</a> <a href="./has-xxx-trait-named-def.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./has-xxx-template-named-def.html" class="navigation-link">Back</a> <a href="./has-xxx-trait-named-def.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./introspection.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="./macros.html" class="navigation-link">Macros</a> / <a href="./introspection.html" class="navigation-link">Introspection</a> / <a href="./has-xxx-trait-def.html" class="navigation-link">BOOST_MPL_HAS_XXX_TRAIT_DEF</a></td> </tr></table><div class="header-separator"></div> <div class="section" id="boost-mpl-has-xxx-trait-def"> <h1><a class="toc-backref" href="./introspection.html#id1595">BOOST_MPL_HAS_XXX_TRAIT_DEF</a></h1> <div class="section" id="id1329"> <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> <pre class="literal-block"> #define <a href="./has-xxx-trait-def.html" class="identifier">BOOST_MPL_HAS_XXX_TRAIT_DEF</a>(name) \ <em>unspecified token sequence</em> \ /**/ </pre> </div> <div class="section" id="id1330"> <h3><a class="subsection-title" href="#description" name="description">Description</a></h3> <p>Expands into a definition of a boolean unary <a class="reference internal" href="./metafunction.html">Metafunction</a> <tt class="literal"><span class="pre">has_name</span></tt> such that for any type <tt class="literal"><span class="pre">x</span></tt> <tt class="literal"><span class="pre">has_name<x>::value</span> <span class="pre">==</span> <span class="pre">true</span></tt> if and only if <tt class="literal"><span class="pre">x</span></tt> is a class type and has a nested type memeber <tt class="literal"><span class="pre">x::name</span></tt>.</p> <p>On the deficient compilers not capabale of performing the detection, <tt class="literal"><span class="pre">has_name<x>::value</span></tt> always returns <tt class="literal"><span class="pre">false</span></tt>. A boolean configuraion macro, <a class="reference internal" href="./cfg-no-has-xxx.html">BOOST_MPL_CFG_NO_HAS_XXX</a>, is provided to signal or override the "deficient" status of a particular compiler.</p> <p>[<em>Note:</em> <a class="reference internal" href="./has-xxx-trait-def.html">BOOST_MPL_HAS_XXX_TRAIT_DEF</a> is a simplified front end to the <a class="reference internal" href="./has-xxx-trait-named-def.html">BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF</a> introspection macro — <em>end note</em>]</p> </div> <div class="section" id="id1331"> <h3><a class="subsection-title" href="#header" name="header">Header</a></h3> <pre class="literal-block"> #include <<a href="../../../../boost/mpl/has_xxx.hpp" class="header">boost/mpl/has_xxx.hpp</a>> </pre> </div> <div class="section" id="id1332"> <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> <table border="1" class="docutils table"> <colgroup> <col width="15%" /> <col width="32%" /> <col width="53%" /> </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">name</span></tt></td> <td>A legal identifier token</td> <td>A name of the member being detected.</td> </tr> </tbody> </table> </div> <div class="section" id="id1333"> <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> <p>For any legal C++ identifier <tt class="literal"><span class="pre">name</span></tt>:</p> <pre class="literal-block"> <a href="./has-xxx-trait-def.html" class="identifier">BOOST_MPL_HAS_XXX_TRAIT_DEF</a>(name) </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"><p class="first">Appears at namespace scope.</p> </td> </tr> <tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first">None.</p> </td> </tr> <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p> <pre class="last literal-block"> <a href="./has-xxx-trait-named-def.html" class="identifier">BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF</a>( BOOST_PP_CAT(has_,name), name, false ) </pre> </td> </tr> </tbody> </table> </div> <div class="section" id="id1334"> <h3><a class="subsection-title" href="#example" name="example">Example</a></h3> <pre class="literal-block"> <a href="./has-xxx-trait-def.html" class="identifier">BOOST_MPL_HAS_XXX_TRAIT_DEF</a>(xxx) struct test1 {}; struct test2 { void xxx(); }; struct test3 { int xxx; }; struct test4 { static int xxx(); }; struct test5 { template< typename T > struct xxx {}; }; struct test6 { typedef int xxx; }; struct test7 { struct xxx; }; struct test8 { typedef void (*xxx)(); }; struct test9 { typedef void (xxx)(); }; <a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test1> )); <a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test2> )); <a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test3> )); <a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test4> )); <a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test5> )); #if !defined(<a href="./cfg-no-has-xxx.html" class="identifier">BOOST_MPL_CFG_NO_HAS_XXX</a>) <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test6> )); <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test7> )); <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test8> )); <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test9> )); #endif <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test6,<a href="./bool.html" class="identifier">true_</a>> )); <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test7,<a href="./bool.html" class="identifier">true_</a>> )); <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test8,<a href="./bool.html" class="identifier">true_</a>> )); <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test9,<a href="./bool.html" class="identifier">true_</a>> )); </pre> </div> <div class="section" id="id1335"> <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> <p><a class="reference internal" href="./macros.html">Macros</a>, <a class="reference internal" href="./has-xxx-trait-named-def.html">BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF</a>, <a class="reference internal" href="./cfg-no-has-xxx.html">BOOST_MPL_CFG_NO_HAS_XXX</a></p> <!-- Macros/Introspection//BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF --> </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="./has-xxx-template-named-def.html" class="navigation-link">Prev</a> <a href="./has-xxx-trait-named-def.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./has-xxx-template-named-def.html" class="navigation-link">Back</a> <a href="./has-xxx-trait-named-def.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./introspection.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><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> </html>