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_TEMPLATE_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="./introspection.html" class="navigation-link">Prev</a> <a href="./has-xxx-template-named-def.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group">Back <a href="./has-xxx-template-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-template-def.html" class="navigation-link">BOOST_MPL_HAS_XXX_TEMPLATE_DEF</a></td> 13</tr></table><div class="header-separator"></div> 14<div class="section" id="boost-mpl-has-xxx-template-def"> 15<h1><a class="toc-backref" href="./introspection.html#id1593">BOOST_MPL_HAS_XXX_TEMPLATE_DEF</a></h1> 16<div class="section" id="id1315"> 17<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> 18<pre class="literal-block"> 19#define <a href="./has-xxx-template-def.html" class="identifier">BOOST_MPL_HAS_XXX_TEMPLATE_DEF</a>(name) \ 20 <em>unspecified token sequence</em> \ 21/**/ 22</pre> 23</div> 24<div class="section" id="id1316"> 25<h3><a class="subsection-title" href="#description" name="description">Description</a></h3> 26<p>Expands into the definition of a boolean <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 28only if <tt class="literal"><span class="pre">x</span></tt> is a class type and has a nested template member 29<tt class="literal"><span class="pre">x::template</span> <span class="pre">name</span></tt> with no more than 30<a class="reference internal" href="./limit-metafunction-arity.html">BOOST_MPL_LIMIT_METAFUNCTION_ARITY</a> parameters.</p> 31<p>On deficient compilers not capable of performing the detection, 32<tt class="literal"><span class="pre">has_name<x>::value</span></tt> is always <tt class="literal"><span class="pre">false</span></tt>. A boolean configuration 33macro, <a class="reference internal" href="./cfg-no-has-xxx-template.html">BOOST_MPL_CFG_NO_HAS_XXX_TEMPLATE</a>, is provided to signal or 34override the "deficient" status of a particular compiler.</p> 35<p>[<em>Note:</em> <a class="reference internal" href="./has-xxx-template-def.html">BOOST_MPL_HAS_XXX_TEMPLATE_DEF</a> is a simplified front end to 36the <a class="reference internal" href="./has-xxx-template-named-def.html">BOOST_MPL_HAS_XXX_TEMPLATE_NAMED_DEF</a> introspection macro — <em>end note</em>]</p> 37</div> 38<div class="section" id="id1317"> 39<h3><a class="subsection-title" href="#header" name="header">Header</a></h3> 40<pre class="literal-block"> 41#include <<a href="../../../../boost/mpl/has_xxx.hpp" class="header">boost/mpl/has_xxx.hpp</a>> 42</pre> 43</div> 44<div class="section" id="id1318"> 45<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> 46<table border="1" class="docutils table"> 47<colgroup> 48<col width="15%" /> 49<col width="32%" /> 50<col width="53%" /> 51</colgroup> 52<thead valign="bottom"> 53<tr><th class="head">Parameter</th> 54<th class="head">Requirement</th> 55<th class="head">Description</th> 56</tr> 57</thead> 58<tbody valign="top"> 59<tr><td><tt class="literal"><span class="pre">name</span></tt></td> 60<td>A legal identifier token</td> 61<td>A name of the template member being detected.</td> 62</tr> 63</tbody> 64</table> 65</div> 66<div class="section" id="id1319"> 67<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> 68<p>For any legal C++ identifier <tt class="literal"><span class="pre">name</span></tt>:</p> 69<pre class="literal-block"> 70<a href="./has-xxx-template-def.html" class="identifier">BOOST_MPL_HAS_XXX_TEMPLATE_DEF</a>(name) 71</pre> 72<table class="docutils field-list" frame="void" rules="none"> 73<col class="field-name" /> 74<col class="field-body" /> 75<tbody valign="top"> 76<tr class="field"><th class="field-name">Precondition:</th><td class="field-body"><p class="first">Appears at namespace scope.</p> 77</td> 78</tr> 79<tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first">None.</p> 80</td> 81</tr> 82<tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p> 83<pre class="last literal-block"> 84<a href="./has-xxx-template-named-def.html" class="identifier">BOOST_MPL_HAS_XXX_TEMPLATE_NAMED_DEF</a>( 85 BOOST_PP_CAT(has_,name), name, false 86 ) 87</pre> 88</td> 89</tr> 90</tbody> 91</table> 92</div> 93<div class="section" id="id1320"> 94<h3><a class="subsection-title" href="#example" name="example">Example</a></h3> 95<pre class="literal-block"> 96<a href="./has-xxx-template-def.html" class="identifier">BOOST_MPL_HAS_XXX_TEMPLATE_DEF</a>(xxx) 97 98struct test1 {}; 99struct test2 { void xxx(); }; 100struct test3 { int xxx; }; 101struct test4 { static int xxx(); }; 102struct test5 { typedef int xxx; }; 103struct test6 { struct xxx; }; 104struct test7 { typedef void (*xxx)(); }; 105struct test8 { typedef void (xxx)(); }; 106struct test9 { template< class T > struct xxx {}; }; 107 108<a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test1> )); 109<a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test2> )); 110<a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test3> )); 111<a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test4> )); 112<a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test5> )); 113<a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test6> )); 114<a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test7> )); 115<a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test8> )); 116 117#if !defined(<a href="./cfg-no-has-xxx-template.html" class="identifier">BOOST_MPL_CFG_NO_HAS_XXX_TEMPLATE</a>) 118<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test9> )); 119#endif 120 121<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test9, <a href="./bool.html" class="identifier">true_</a>> )); 122</pre> 123</div> 124<div class="section" id="id1321"> 125<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> 126<p><a class="reference internal" href="./macros.html">Macros</a>, <a class="reference internal" href="./has-xxx-template-named-def.html">BOOST_MPL_HAS_XXX_TEMPLATE_NAMED_DEF</a>, 127<a class="reference internal" href="./cfg-no-has-xxx-template.html">BOOST_MPL_CFG_NO_HAS_XXX_TEMPLATE</a>, <a class="reference internal" href="./limit-metafunction-arity.html">BOOST_MPL_LIMIT_METAFUNCTION_ARITY</a></p> 128<!-- Macros/Introspection//BOOST_MPL_HAS_XXX_TEMPLATE_NAMED_DEF --> 129<!-- Copyright Daniel Walker 2007. --> 130<!-- Distributed under the Boost --> 131<!-- Software License, Version 1.0. 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