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  25. <div class="section">
  26. <div class="titlepage"><div><div><h3 class="title">
  27. <a name="boost_typetraits.reference.extent"></a><a class="link" href="extent.html" title="extent">extent</a>
  28. </h3></div></div></div>
  29. <pre class="programlisting"><span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">N</span> <span class="special">=</span> <span class="number">0</span><span class="special">&gt;</span>
  30. <span class="keyword">struct</span> <span class="identifier">extent</span> <span class="special">:</span> <span class="keyword">public</span> <a class="link" href="integral_constant.html" title="integral_constant">integral_constant</a><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">,</span> <span class="identifier">EXTENT</span><span class="special">(</span><span class="identifier">T</span><span class="special">,</span><span class="identifier">N</span><span class="special">)&gt;</span> <span class="special">{};</span>
  31. </pre>
  32. <p>
  33. <span class="bold"><strong>Inherits:</strong></span> Class template extent inherits
  34. from <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">integral_constant</a><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">,</span> <span class="identifier">EXTENT</span><span class="special">(</span><span class="identifier">T</span><span class="special">,</span><span class="identifier">N</span><span class="special">)&gt;</span></code>,
  35. where <code class="computeroutput"><span class="identifier">EXTENT</span><span class="special">(</span><span class="identifier">T</span><span class="special">,</span><span class="identifier">N</span><span class="special">)</span></code> is the number of elements in the N'th array
  36. dimension of type <code class="computeroutput"><span class="identifier">T</span></code>.
  37. </p>
  38. <p>
  39. If <code class="computeroutput"><span class="identifier">T</span></code> is not a (built-in)
  40. array type, or if <code class="computeroutput"><span class="identifier">N</span> <span class="special">&gt;</span>
  41. <a class="link" href="rank.html" title="rank">rank</a><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">value</span></code>, or if the N'th array bound is incomplete,
  42. then <code class="computeroutput"><span class="identifier">EXTENT</span><span class="special">(</span><span class="identifier">T</span><span class="special">,</span><span class="identifier">N</span><span class="special">)</span></code> is zero.
  43. </p>
  44. <p>
  45. <span class="bold"><strong>Header:</strong></span> <code class="computeroutput"> <span class="preprocessor">#include</span>
  46. <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">/</span><span class="identifier">extent</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
  47. or <code class="computeroutput"> <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
  48. </p>
  49. <p>
  50. <span class="bold"><strong>Examples:</strong></span>
  51. </p>
  52. <div class="blockquote"><blockquote class="blockquote"><p>
  53. <code class="computeroutput"><span class="identifier">extent</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">[</span><span class="number">1</span><span class="special">]&gt;</span></code> inherits from <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">integral_constant</a><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">,</span> <span class="number">1</span><span class="special">&gt;</span></code>.
  54. </p></blockquote></div>
  55. <div class="blockquote"><blockquote class="blockquote"><p>
  56. <code class="computeroutput"><span class="identifier">extent</span><span class="special">&lt;</span><span class="keyword">double</span><span class="special">[</span><span class="number">2</span><span class="special">][</span><span class="number">3</span><span class="special">][</span><span class="number">4</span><span class="special">],</span>
  57. <span class="number">0</span><span class="special">&gt;::</span><span class="identifier">type</span></code> is the type <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">integral_constant</a><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">,</span> <span class="number">2</span><span class="special">&gt;</span></code>.
  58. </p></blockquote></div>
  59. <div class="blockquote"><blockquote class="blockquote"><p>
  60. <code class="computeroutput"><span class="identifier">extent</span><span class="special">&lt;</span><span class="keyword">double</span><span class="special">[</span><span class="number">2</span><span class="special">][</span><span class="number">3</span><span class="special">][</span><span class="number">4</span><span class="special">],</span>
  61. <span class="number">1</span><span class="special">&gt;::</span><span class="identifier">type</span></code> is the type <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">integral_constant</a><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">,</span> <span class="number">3</span><span class="special">&gt;</span></code>.
  62. </p></blockquote></div>
  63. <div class="blockquote"><blockquote class="blockquote"><p>
  64. <code class="computeroutput"><span class="identifier">extent</span><span class="special">&lt;</span><span class="keyword">double</span><span class="special">[</span><span class="number">2</span><span class="special">][</span><span class="number">3</span><span class="special">][</span><span class="number">4</span><span class="special">],</span>
  65. <span class="number">2</span><span class="special">&gt;::</span><span class="identifier">type</span></code> is the type <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">integral_constant</a><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">,</span> <span class="number">4</span><span class="special">&gt;</span></code>.
  66. </p></blockquote></div>
  67. <div class="blockquote"><blockquote class="blockquote"><p>
  68. <code class="computeroutput"><span class="identifier">extent</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">[</span><span class="number">4</span><span class="special">]&gt;::</span><span class="identifier">value</span></code>
  69. is an integral constant expression that evaluates to <span class="emphasis"><em>4</em></span>.
  70. </p></blockquote></div>
  71. <div class="blockquote"><blockquote class="blockquote"><p>
  72. <code class="computeroutput"><span class="identifier">extent</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">[][</span><span class="number">2</span><span class="special">]&gt;::</span><span class="identifier">value</span></code>
  73. is an integral constant expression that evaluates to <span class="emphasis"><em>0</em></span>.
  74. </p></blockquote></div>
  75. <div class="blockquote"><blockquote class="blockquote"><p>
  76. <code class="computeroutput"><span class="identifier">extent</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">[][</span><span class="number">2</span><span class="special">],</span> <span class="number">1</span><span class="special">&gt;::</span><span class="identifier">value</span></code> is an integral constant expression
  77. that evaluates to <span class="emphasis"><em>2</em></span>.
  78. </p></blockquote></div>
  79. <div class="blockquote"><blockquote class="blockquote"><p>
  80. <code class="computeroutput"><span class="identifier">extent</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">*&gt;::</span><span class="identifier">value</span></code> is an integral constant expression
  81. that evaluates to <span class="emphasis"><em>0</em></span>.
  82. </p></blockquote></div>
  83. <div class="blockquote"><blockquote class="blockquote"><p>
  84. <code class="computeroutput"><span class="identifier">extent</span><span class="special">&lt;</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">array</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span> <span class="number">3</span><span class="special">&gt;</span> <span class="special">&gt;::</span><span class="identifier">value</span></code> is an integral constant expression
  85. that evaluates to <span class="emphasis"><em>0</em></span>: <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">array</span></code>
  86. is a class type and <span class="bold"><strong>not an array type</strong></span>!
  87. </p></blockquote></div>
  88. <div class="blockquote"><blockquote class="blockquote"><p>
  89. <code class="computeroutput"><span class="identifier">extent</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">value_type</span></code> is the type <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span></code>.
  90. </p></blockquote></div>
  91. <p>
  92. <span class="bold"><strong>Compiler Compatibility:</strong></span> All current compilers
  93. are supported by this trait.
  94. </p>
  95. </div>
  96. <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
  97. <td align="left"></td>
  98. <td align="right"><div class="copyright-footer">Copyright &#169; 2000, 2011 Adobe Systems Inc, David Abrahams,
  99. Frederic Bron, Steve Cleary, Beman Dawes, Aleksey Gurtovoy, Howard Hinnant,
  100. Jesse Jones, Mat Marcus, Itay Maman, John Maddock, Alexander Nasonov, Thorsten
  101. Ottosen, Roman Perepelitsa, Robert Ramey, Jeremy Siek, Robert Stewart and Steven
  102. Watanabe<p>
  103. Distributed under the Boost Software License, Version 1.0. (See accompanying
  104. file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
  105. </p>
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