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  7. <title>The MPL Reference Manual: Forward Sequence</title>
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  12. <td class="header-group page-location"><a href="../refmanual.html" class="navigation-link">Front Page</a> / <a href="./sequences.html" class="navigation-link">Sequences</a> / <a href="./concepts.html" class="navigation-link">Concepts</a> / <a href="./forward-sequence.html" class="navigation-link">Forward Sequence</a></td>
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  14. <div class="section" id="forward-sequence">
  15. <h1><a class="toc-backref" href="./concepts.html#id1395">Forward Sequence</a></h1>
  16. <div class="section" id="description">
  17. <h3>Description</h3>
  18. <p>A <a class="reference internal" href="./forward-sequence.html">Forward Sequence</a> is an MPL concept representing a compile-time sequence of
  19. elements. Sequence elements are
  20. types, and are accessible through <a class="reference internal" href="./iterators.html">Iterators</a>. The <a class="reference internal" href="./begin.html">begin</a> and <a class="reference internal" href="./end.html">end</a> metafunctions
  21. provide iterators delimiting the range of the sequence
  22. elements. A sequence guarantees that its elements are arranged in a definite,
  23. but possibly unspecified, order. Every MPL sequence is a <a class="reference internal" href="./forward-sequence.html">Forward Sequence</a>.</p>
  24. </div>
  25. <div class="section" id="definitions">
  26. <h3>Definitions</h3>
  27. <ul class="simple">
  28. <li>The <em>size</em> of a sequence is the number of elements it contains. The size is a
  29. nonnegative number.</li>
  30. <li>A sequence is <em>empty</em> if its size is zero.</li>
  31. </ul>
  32. </div>
  33. <div class="section" id="expression-requirements">
  34. <h3>Expression requirements</h3>
  35. <p>For any <a class="reference internal" href="./forward-sequence.html">Forward Sequence</a> <tt class="literal"><span class="pre">s</span></tt> the following expressions must be valid:</p>
  36. <table border="1" class="docutils table">
  37. <colgroup>
  38. <col width="30%" />
  39. <col width="39%" />
  40. <col width="30%" />
  41. </colgroup>
  42. <thead valign="bottom">
  43. <tr><th class="head">Expression</th>
  44. <th class="head">Type</th>
  45. <th class="head">Complexity</th>
  46. </tr>
  47. </thead>
  48. <tbody valign="top">
  49. <tr><td><tt class="literal"><span class="pre"><a href="./begin.html" class="identifier">begin</a>&lt;s&gt;::type</span></tt></td>
  50. <td><a class="reference internal" href="./forward-iterator.html">Forward Iterator</a></td>
  51. <td>Amortized constant time</td>
  52. </tr>
  53. <tr><td><tt class="literal"><span class="pre"><a href="./end.html" class="identifier">end</a>&lt;s&gt;::type</span></tt></td>
  54. <td><a class="reference internal" href="./forward-iterator.html">Forward Iterator</a></td>
  55. <td>Amortized constant time</td>
  56. </tr>
  57. <tr><td><tt class="literal"><span class="pre"><a href="./size.html" class="identifier">size</a>&lt;s&gt;::type</span></tt></td>
  58. <td><a class="reference internal" href="./integral-constant.html">Integral Constant</a></td>
  59. <td>Unspecified</td>
  60. </tr>
  61. <tr><td><tt class="literal"><span class="pre"><a href="./empty.html" class="identifier">empty</a>&lt;s&gt;::type</span></tt></td>
  62. <td>Boolean <a class="reference internal" href="./integral-constant.html">Integral Constant</a></td>
  63. <td>Constant time</td>
  64. </tr>
  65. <tr><td><tt class="literal"><span class="pre"><a href="./front.html" class="identifier">front</a>&lt;s&gt;::type</span></tt></td>
  66. <td>Any type</td>
  67. <td>Amortized constant time</td>
  68. </tr>
  69. </tbody>
  70. </table>
  71. </div>
  72. <div class="section" id="expression-semantics">
  73. <h3>Expression semantics</h3>
  74. <table border="1" class="docutils table">
  75. <colgroup>
  76. <col width="28%" />
  77. <col width="72%" />
  78. </colgroup>
  79. <thead valign="bottom">
  80. <tr><th class="head">Expression</th>
  81. <th class="head">Semantics</th>
  82. </tr>
  83. </thead>
  84. <tbody valign="top">
  85. <tr><td><tt class="literal"><span class="pre"><a href="./begin.html" class="identifier">begin</a>&lt;s&gt;::type</span></tt></td>
  86. <td>An iterator to the first element of the sequence; see <a class="reference internal" href="./begin.html">begin</a>.</td>
  87. </tr>
  88. <tr><td><tt class="literal"><span class="pre"><a href="./end.html" class="identifier">end</a>&lt;s&gt;::type</span></tt></td>
  89. <td>A past-the-end iterator to the sequence; see <a class="reference internal" href="./end.html">end</a>.</td>
  90. </tr>
  91. <tr><td><tt class="literal"><span class="pre"><a href="./size.html" class="identifier">size</a>&lt;s&gt;::type</span></tt></td>
  92. <td>The size of the sequence; see <a class="reference internal" href="./size.html">size</a>.</td>
  93. </tr>
  94. <tr><td><tt class="literal"><span class="pre"><a href="./empty.html" class="identifier">empty</a>&lt;s&gt;::type</span></tt></td>
  95. <td>A boolean <a class="reference internal" href="./integral-constant.html">Integral Constant</a> <tt class="literal"><span class="pre">c</span></tt> such that
  96. <tt class="literal"><span class="pre">c::value</span> <span class="pre">==</span> <span class="pre">true</span></tt> if and only if the sequence is empty; see <a class="reference internal" href="./empty.html">empty</a>.</td>
  97. </tr>
  98. <tr><td><tt class="literal"><span class="pre"><a href="./front.html" class="identifier">front</a>&lt;s&gt;::type</span></tt></td>
  99. <td>The first element in the sequence; see <a class="reference internal" href="./front.html">front</a>.</td>
  100. </tr>
  101. </tbody>
  102. </table>
  103. </div>
  104. <div class="section" id="invariants">
  105. <h3>Invariants</h3>
  106. <p>For any <a class="reference internal" href="./forward-sequence.html">Forward Sequence</a> <tt class="literal"><span class="pre">s</span></tt> the following invariants always hold:</p>
  107. <ul class="simple">
  108. <li>[<tt class="literal"><span class="pre"><a href="./begin.html" class="identifier">begin</a>&lt;s&gt;::type</span></tt>, <tt class="literal"><span class="pre"><a href="./end.html" class="identifier">end</a>&lt;s&gt;::type</span></tt>) is always a valid range.</li>
  109. <li>An algorithm that iterates through the range [<tt class="literal"><span class="pre"><a href="./begin.html" class="identifier">begin</a>&lt;s&gt;::type</span></tt>, <tt class="literal"><span class="pre"><a href="./end.html" class="identifier">end</a>&lt;s&gt;::type</span></tt>)
  110. will pass through every element of <tt class="literal"><span class="pre">s</span></tt> exactly once.</li>
  111. <li><tt class="literal"><span class="pre"><a href="./begin.html" class="identifier">begin</a>&lt;s&gt;::type</span></tt> is identical to <tt class="literal"><span class="pre"><a href="./end.html" class="identifier">end</a>&lt;s&gt;::type</span></tt> if and only if <tt class="literal"><span class="pre">s</span></tt> is empty.</li>
  112. <li>Two different iterations through <tt class="literal"><span class="pre">s</span></tt> will access its elements in the same order.</li>
  113. </ul>
  114. </div>
  115. <div class="section" id="models">
  116. <h3>Models</h3>
  117. <ul class="simple">
  118. <li><a class="reference internal" href="./vector.html">vector</a></li>
  119. <li><a class="reference internal" href="./map.html">map</a></li>
  120. <li><a class="reference internal" href="./range-c.html">range_c</a></li>
  121. <li><a class="reference internal" href="./iterator-range.html">iterator_range</a></li>
  122. <li><a class="reference internal" href="./filter-view.html">filter_view</a></li>
  123. </ul>
  124. </div>
  125. <div class="section" id="see-also">
  126. <h3>See also</h3>
  127. <p><a class="reference internal" href="./sequences.html">Sequences</a>, <a class="reference internal" href="./bidirectional-sequence.html">Bidirectional Sequence</a>, <a class="reference internal" href="./forward-iterator.html">Forward Iterator</a>, <a class="reference internal" href="./begin.html">begin</a> / <a class="reference internal" href="./end.html">end</a>, <a class="reference internal" href="./size.html">size</a>, <a class="reference internal" href="./empty.html">empty</a>, <a class="reference internal" href="./front.html">front</a></p>
  128. <!-- Sequences/Concepts//Bidirectional Sequence |20 -->
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  133. <td><div class="copyright-footer"><div class="copyright">Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams</div>
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