sizeof.html 7.3 KB

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  7. <title>The MPL Reference Manual: sizeof_</title>
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  14. <div class="section" id="sizeof">
  15. <h1><a class="toc-backref" href="./miscellaneous.html#id1571">sizeof_</a></h1>
  16. <div class="section" id="id1207">
  17. <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
  18. <pre class="literal-block">
  19. template&lt;
  20. typename X
  21. &gt;
  22. struct <a href="./sizeof.html" class="identifier">sizeof_</a>
  23. {
  24. typedef <em>unspecified</em> type;
  25. };
  26. </pre>
  27. </div>
  28. <div class="section" id="id1208">
  29. <h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
  30. <p>Returns the result of a <tt class="literal"><span class="pre">sizeof(X)</span></tt> expression wrapped into an
  31. <a class="reference internal" href="./integral-constant.html">Integral Constant</a> of the corresponding type, <tt class="literal"><span class="pre">std::<a href="./size-t.html" class="identifier">size_t</a></span></tt>.</p>
  32. </div>
  33. <div class="section" id="id1209">
  34. <h3><a class="subsection-title" href="#header" name="header">Header</a></h3>
  35. <pre class="literal-block">
  36. #include &lt;<a href="../../../../boost/mpl/sizeof.hpp" class="header">boost/mpl/sizeof.hpp</a>&gt;
  37. </pre>
  38. </div>
  39. <div class="section" id="id1210">
  40. <h3><a class="subsection-title" href="#model-of" name="model-of">Model of</a></h3>
  41. <p><a class="reference internal" href="./metafunction.html">Metafunction</a></p>
  42. </div>
  43. <div class="section" id="id1211">
  44. <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3>
  45. <table border="1" class="docutils table">
  46. <colgroup>
  47. <col width="19%" />
  48. <col width="25%" />
  49. <col width="56%" />
  50. </colgroup>
  51. <thead valign="bottom">
  52. <tr><th class="head">Parameter</th>
  53. <th class="head">Requirement</th>
  54. <th class="head">Description</th>
  55. </tr>
  56. </thead>
  57. <tbody valign="top">
  58. <tr><td><tt class="literal"><span class="pre">X</span></tt></td>
  59. <td>Any type</td>
  60. <td>A type to compute the <tt class="literal"><span class="pre">sizeof</span></tt> for.</td>
  61. </tr>
  62. </tbody>
  63. </table>
  64. </div>
  65. <div class="section" id="id1212">
  66. <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
  67. <p>For an arbitrary type <tt class="literal"><span class="pre">x</span></tt>:</p>
  68. <pre class="literal-block">
  69. typedef <a href="./sizeof.html" class="identifier">sizeof_</a>&lt;x&gt;::type n;
  70. </pre>
  71. <table class="docutils field-list" frame="void" rules="none">
  72. <col class="field-name" />
  73. <col class="field-body" />
  74. <tbody valign="top">
  75. <tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first"><a class="reference internal" href="./integral-constant.html">Integral Constant</a>.</p>
  76. </td>
  77. </tr>
  78. <tr class="field"><th class="field-name">Precondition:</th><td class="field-body"><p class="first"><tt class="literal"><span class="pre">x</span></tt> is a complete type.</p>
  79. </td>
  80. </tr>
  81. <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p>
  82. <pre class="last literal-block">
  83. typedef <a href="./size-t.html" class="identifier">size_t</a>&lt; sizeof(x) &gt; n;
  84. </pre>
  85. </td>
  86. </tr>
  87. </tbody>
  88. </table>
  89. </div>
  90. <div class="section" id="id1213">
  91. <h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3>
  92. <p>Constant time.</p>
  93. </div>
  94. <div class="section" id="id1214">
  95. <h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
  96. <pre class="literal-block">
  97. struct udt { char a[100]; };
  98. <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( <a href="./sizeof.html" class="identifier">sizeof_</a>&lt;char&gt;::value, ==, sizeof(char) );
  99. <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( <a href="./sizeof.html" class="identifier">sizeof_</a>&lt;int&gt;::value, ==, sizeof(int) );
  100. <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( <a href="./sizeof.html" class="identifier">sizeof_</a>&lt;double&gt;::value, ==, sizeof(double) );
  101. <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( <a href="./sizeof.html" class="identifier">sizeof_</a>&lt;udt&gt;::value, ==, sizeof(my) );
  102. </pre>
  103. </div>
  104. <div class="section" id="id1215">
  105. <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
  106. <p><a class="reference internal" href="./metafunctions.html">Metafunctions</a>, <a class="reference internal" href="./integral-constant.html">Integral Constant</a>, <a class="reference internal" href="./size-t.html">size_t</a></p>
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