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7 <title>The MPL Reference Manual: BOOST_MPL_HAS_XXX_TRAIT_DEF
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14 <div class=
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"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> \
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>
27 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
28 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>
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
31 macro,
<a class=
"reference internal" href=
"./cfg-no-has-xxx.html">BOOST_MPL_CFG_NO_HAS_XXX
</a>, is provided to signal or override
32 the
"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
34 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>
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>>
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">
50 <thead valign=
"bottom">
51 <tr><th class=
"head">Parameter
</th>
52 <th class=
"head">Requirement
</th>
53 <th class=
"head">Description
</th>
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>
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)
70 <table class=
"docutils field-list" frame=
"void" rules=
"none">
71 <col class=
"field-name" />
72 <col class=
"field-body" />
74 <tr class=
"field"><th class=
"field-name">Precondition:
</th><td class=
"field-body"><p class=
"first">Appears at namespace scope.
</p>
77 <tr class=
"field"><th class=
"field-name">Return type:
</th><td class=
"field-body"><p class=
"first">None.
</p>
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
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)
97 struct test2 { void xxx(); };
98 struct test3 { int xxx; };
99 struct test4 { static int xxx(); };
100 struct test5 { template
< typename T
> struct xxx {}; };
101 struct test6 { typedef int xxx; };
102 struct test7 { struct xxx; };
103 struct test8 { typedef void (*xxx)(); };
104 struct test9 { typedef void (xxx)(); };
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
> ));
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
> ));
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>> ));
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 -->
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134 <td><div class=
"copyright-footer"><div class=
"copyright">Copyright ©
2001-
2009 Aleksey Gurtovoy and David Abrahams
</div>
135 Distributed under the Boost Software License, Version
1.0. (See accompanying
136 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
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