138 lines
9.4 KiB
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138 lines
9.4 KiB
HTML
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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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<meta name="generator" content="Docutils 0.7: http://docutils.sourceforge.net/" />
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<title>The MPL Reference Manual: BOOST_MPL_HAS_XXX_TRAIT_DEF</title>
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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="./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>
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<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>
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</tr></table><div class="header-separator"></div>
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<div class="section" id="boost-mpl-has-xxx-trait-def">
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<h1><a class="toc-backref" href="./introspection.html#id1595">BOOST_MPL_HAS_XXX_TRAIT_DEF</a></h1>
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<div class="section" id="id1329">
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<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
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<pre class="literal-block">
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#define <a href="./has-xxx-trait-def.html" class="identifier">BOOST_MPL_HAS_XXX_TRAIT_DEF</a>(name) \
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<em>unspecified token sequence</em> \
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/**/
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</pre>
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</div>
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<div class="section" id="id1330">
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<h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
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<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>
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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
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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>
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<p>On the deficient compilers not capabale of performing the detection,
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<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
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macro, <a class="reference internal" href="./cfg-no-has-xxx.html">BOOST_MPL_CFG_NO_HAS_XXX</a>, is provided to signal or override
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the "deficient" status of a particular compiler.</p>
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<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
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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>
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</div>
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<div class="section" id="id1331">
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<h3><a class="subsection-title" href="#header" name="header">Header</a></h3>
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<pre class="literal-block">
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#include <<a href="../../../../boost/mpl/has_xxx.hpp" class="header">boost/mpl/has_xxx.hpp</a>>
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</pre>
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</div>
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<div class="section" id="id1332">
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<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3>
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<table border="1" class="docutils table">
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<colgroup>
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<col width="15%" />
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<col width="32%" />
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<col width="53%" />
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</colgroup>
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<thead valign="bottom">
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<tr><th class="head">Parameter</th>
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<th class="head">Requirement</th>
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<th class="head">Description</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</span></tt></td>
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<td>A legal identifier token</td>
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<td>A name of the member being detected.</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="id1333">
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<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
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<p>For any legal C++ identifier <tt class="literal"><span class="pre">name</span></tt>:</p>
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<pre class="literal-block">
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<a href="./has-xxx-trait-def.html" class="identifier">BOOST_MPL_HAS_XXX_TRAIT_DEF</a>(name)
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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"><p class="first">Appears at namespace scope.</p>
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</td>
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</tr>
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<tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first">None.</p>
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</td>
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</tr>
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<tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p>
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<pre class="last literal-block">
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<a href="./has-xxx-trait-named-def.html" class="identifier">BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF</a>(
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BOOST_PP_CAT(has_,name), name, false
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)
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</pre>
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</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="id1334">
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<h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
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<pre class="literal-block">
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<a href="./has-xxx-trait-def.html" class="identifier">BOOST_MPL_HAS_XXX_TRAIT_DEF</a>(xxx)
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struct test1 {};
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struct test2 { void xxx(); };
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struct test3 { int xxx; };
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struct test4 { static int xxx(); };
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struct test5 { template< typename T > struct xxx {}; };
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struct test6 { typedef int xxx; };
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struct test7 { struct xxx; };
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struct test8 { typedef void (*xxx)(); };
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struct test9 { typedef void (xxx)(); };
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<a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test1> ));
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<a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test2> ));
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<a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test3> ));
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<a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test4> ));
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<a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx<test5> ));
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#if !defined(<a href="./cfg-no-has-xxx.html" class="identifier">BOOST_MPL_CFG_NO_HAS_XXX</a>)
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<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test6> ));
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<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test7> ));
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<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test8> ));
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<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test9> ));
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#endif
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<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test6,<a href="./bool.html" class="identifier">true_</a>> ));
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<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test7,<a href="./bool.html" class="identifier">true_</a>> ));
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<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test8,<a href="./bool.html" class="identifier">true_</a>> ));
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<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx<test9,<a href="./bool.html" class="identifier">true_</a>> ));
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</pre>
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</div>
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<div class="section" id="id1335">
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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="./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>
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<!-- Macros/Introspection//BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF -->
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</div>
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</div>
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<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>
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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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