has-xxx-template-def.html 9.2 KB

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  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>
  27. such that for any type <tt class="literal"><span class="pre">x</span></tt> <tt class="literal"><span class="pre">has_name&lt;x&gt;::value</span> <span class="pre">==</span> <span class="pre">true</span></tt> if and
  28. only 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&lt;x&gt;::value</span></tt> is always <tt class="literal"><span class="pre">false</span></tt>. A boolean configuration
  33. macro, <a class="reference internal" href="./cfg-no-has-xxx-template.html">BOOST_MPL_CFG_NO_HAS_XXX_TEMPLATE</a>, is provided to signal or
  34. override the &quot;deficient&quot; 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
  36. the <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 &lt;<a href="../../../../boost/mpl/has_xxx.hpp" class="header">boost/mpl/has_xxx.hpp</a>&gt;
  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. struct test1 {};
  98. struct test2 { void xxx(); };
  99. struct test3 { int xxx; };
  100. struct test4 { static int xxx(); };
  101. struct test5 { typedef int xxx; };
  102. struct test6 { struct xxx; };
  103. struct test7 { typedef void (*xxx)(); };
  104. struct test8 { typedef void (xxx)(); };
  105. struct test9 { template&lt; class T &gt; struct xxx {}; };
  106. <a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx&lt;test1&gt; ));
  107. <a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx&lt;test2&gt; ));
  108. <a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx&lt;test3&gt; ));
  109. <a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx&lt;test4&gt; ));
  110. <a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx&lt;test5&gt; ));
  111. <a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx&lt;test6&gt; ));
  112. <a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx&lt;test7&gt; ));
  113. <a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( has_xxx&lt;test8&gt; ));
  114. #if !defined(<a href="./cfg-no-has-xxx-template.html" class="identifier">BOOST_MPL_CFG_NO_HAS_XXX_TEMPLATE</a>)
  115. <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx&lt;test9&gt; ));
  116. #endif
  117. <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( has_xxx&lt;test9, <a href="./bool.html" class="identifier">true_</a>&gt; ));
  118. </pre>
  119. </div>
  120. <div class="section" id="id1321">
  121. <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
  122. <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>,
  123. <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>
  124. <!-- Macros/Introspection//BOOST_MPL_HAS_XXX_TEMPLATE_NAMED_DEF -->
  125. <!-- Copyright Daniel Walker 2007. -->
  126. <!-- Distributed under the Boost -->
  127. <!-- Software License, Version 1.0. (See accompanying -->
  128. <!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
  129. </div>
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