1<?xml version="1.0" encoding="utf-8" ?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> 4<head> 5<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 6<meta name="generator" content="Docutils 0.7: http://docutils.sourceforge.net/" /> 7<title>The MPL Reference Manual: BOOST_MPL_HAS_XXX_TRAIT_DEF</title> 8<link rel="stylesheet" href="../style.css" type="text/css" /> 9</head> 10<body class="docframe refmanual"> 11<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> 12<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> 13</tr></table><div class="header-separator"></div> 14<div class="section" id="boost-mpl-has-xxx-trait-def"> 15<h1><a class="toc-backref" href="./introspection.html#id1595">BOOST_MPL_HAS_XXX_TRAIT_DEF</a></h1> 16<div class="section" id="id1329"> 17<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> 18<pre class="literal-block"> 19#define <a href="./has-xxx-trait-def.html" class="identifier">BOOST_MPL_HAS_XXX_TRAIT_DEF</a>(name) \ 20 <em>unspecified token sequence</em> \ 21/**/ 22</pre> 23</div> 24<div class="section" id="id1330"> 25<h3><a class="subsection-title" href="#description" name="description">Description</a></h3> 26<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> 27such 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 28if <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> 29<p>On the deficient compilers not capabale of performing the detection, 30<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 31macro, <a class="reference internal" href="./cfg-no-has-xxx.html">BOOST_MPL_CFG_NO_HAS_XXX</a>, is provided to signal or override 32the "deficient" status of a particular compiler.</p> 33<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 34the <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> 35</div> 36<div class="section" id="id1331"> 37<h3><a class="subsection-title" href="#header" name="header">Header</a></h3> 38<pre class="literal-block"> 39#include <<a href="../../../../boost/mpl/has_xxx.hpp" class="header">boost/mpl/has_xxx.hpp</a>> 40</pre> 41</div> 42<div class="section" id="id1332"> 43<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> 44<table border="1" class="docutils table"> 45<colgroup> 46<col width="15%" /> 47<col width="32%" /> 48<col width="53%" /> 49</colgroup> 50<thead valign="bottom"> 51<tr><th class="head">Parameter</th> 52<th class="head">Requirement</th> 53<th class="head">Description</th> 54</tr> 55</thead> 56<tbody valign="top"> 57<tr><td><tt class="literal"><span class="pre">name</span></tt></td> 58<td>A legal identifier token</td> 59<td>A name of the member being detected.</td> 60</tr> 61</tbody> 62</table> 63</div> 64<div class="section" id="id1333"> 65<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> 66<p>For any legal C++ identifier <tt class="literal"><span class="pre">name</span></tt>:</p> 67<pre class="literal-block"> 68<a href="./has-xxx-trait-def.html" class="identifier">BOOST_MPL_HAS_XXX_TRAIT_DEF</a>(name) 69</pre> 70<table class="docutils field-list" frame="void" rules="none"> 71<col class="field-name" /> 72<col class="field-body" /> 73<tbody valign="top"> 74<tr class="field"><th class="field-name">Precondition:</th><td class="field-body"><p class="first">Appears at namespace scope.</p> 75</td> 76</tr> 77<tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first">None.</p> 78</td> 79</tr> 80<tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p> 81<pre class="last literal-block"> 82<a href="./has-xxx-trait-named-def.html" class="identifier">BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF</a>( 83 BOOST_PP_CAT(has_,name), name, false 84 ) 85</pre> 86</td> 87</tr> 88</tbody> 89</table> 90</div> 91<div class="section" id="id1334"> 92<h3><a class="subsection-title" href="#example" name="example">Example</a></h3> 93<pre class="literal-block"> 94<a href="./has-xxx-trait-def.html" class="identifier">BOOST_MPL_HAS_XXX_TRAIT_DEF</a>(xxx) 95 96struct test1 {}; 97struct test2 { void xxx(); }; 98struct test3 { int xxx; }; 99struct test4 { static int xxx(); }; 100struct test5 { template< typename T > struct xxx {}; }; 101struct test6 { typedef int xxx; }; 102struct test7 { struct xxx; }; 103struct test8 { typedef void (*xxx)(); }; 104struct test9 { typedef void (xxx)(); }; 105 106<a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test1> )); 107<a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test2> )); 108<a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test3> )); 109<a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test4> )); 110<a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test5> )); 111 112#if !defined(<a href="./cfg-no-has-xxx.html" class="identifier">BOOST_MPL_CFG_NO_HAS_XXX</a>) 113<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test6> )); 114<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test7> )); 115<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test8> )); 116<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test9> )); 117#endif 118 119<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test6,<a href="./bool.html" class="identifier">true_</a>> )); 120<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test7,<a href="./bool.html" class="identifier">true_</a>> )); 121<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test8,<a href="./bool.html" class="identifier">true_</a>> )); 122<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test9,<a href="./bool.html" class="identifier">true_</a>> )); 123</pre> 124</div> 125<div class="section" id="id1335"> 126<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> 127<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> 128<!-- Macros/Introspection//BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF --> 129</div> 130</div> 131 132<div class="footer-separator"></div> 133<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> 134<td><div class="copyright-footer"><div class="copyright">Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams</div> 135Distributed under the Boost Software License, Version 1.0. (See accompanying 136file 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> 137</html> 138