ceph/src/boost/libs/mpl/doc/refmanual/associative-sequence.html

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   7 <title>The MPL Reference Manual: Associative Sequence</title>
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  14 <div class="section" id="associative-sequence">
  15 <h1><a class="toc-backref" href="./concepts.html#id1401">Associative Sequence</a></h1>
  16 <div class="section" id="id29">
  17 <h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
  18 <p>An <a class="reference internal" href="./associative-sequence.html">Associative Sequence</a> is a <a class="reference internal" href="./forward-sequence.html">Forward Sequence</a> that allows efficient retrieval of
  19 elements based on keys. Unlike associative containers in the C++ Standard Library,
  20 MPL associative sequences have no associated ordering relation. Instead,
  21 <em>type identity</em> is used to impose an equivalence relation on keys, and the
  22 order in which sequence elements are traversed during iteration is left
  23 unspecified.</p>
  24 </div>
  25 <div class="section" id="id30">
  26 <h3><a class="subsection-title" href="#definitions" name="definitions">Definitions</a></h3>
  27 <ul class="simple" id="value-part">
  28 <span id="key-part"></span><li>A <em>key</em> is a part of the element type used to identify and retrieve
  29 the element within the sequence.</li>
  30 <li>A <em>value</em> is a part of the element type retrievied from the sequence
  31 by its key.</li>
  32 </ul>
  33 </div>
  34 <div class="section" id="id31">
  35 <h3><a class="subsection-title" href="#expression-requirements" name="expression-requirements">Expression requirements</a></h3>
  36 <p>In the following table and subsequent specifications, <tt class="literal"><span class="pre">s</span></tt> is an <a class="reference internal" href="./associative-sequence.html">Associative Sequence</a>,
  37 <tt class="literal"><span class="pre">x</span></tt> is a sequence element, and <tt class="literal"><span class="pre">k</span></tt> and <tt class="literal"><span class="pre">def</span></tt> are arbitrary types.</p>
  38 <p>In addition to the requirements defined in <a class="reference internal" href="./forward-sequence.html">Forward Sequence</a>,
  39 the following must be met:</p>
  40 <table border="1" class="docutils table">
  41 <colgroup>
  42 <col width="33%" />
  43 <col width="38%" />
  44 <col width="29%" />
  45 </colgroup>
  46 <thead valign="bottom">
  47 <tr><th class="head">Expression</th>
  48 <th class="head">Type</th>
  49 <th class="head">Complexity</th>
  50 </tr>
  51 </thead>
  52 <tbody valign="top">
  53 <tr><td><tt class="literal"><span class="pre"><a href="./has-key.html" class="identifier">has_key</a>&lt;s,k&gt;::type</span></tt></td>
  54 <td>Boolean <a class="reference internal" href="./integral-constant.html">Integral Constant</a></td>
  55 <td>Amortized constant time</td>
  56 </tr>
  57 <tr><td><tt class="literal"><span class="pre"><a href="./count.html" class="identifier">count</a>&lt;s,k&gt;::type</span></tt></td>
  58 <td><a class="reference internal" href="./integral-constant.html">Integral Constant</a></td>
  59 <td>Amortized constant time</td>
  60 </tr>
  61 <tr><td><tt class="literal"><span class="pre"><a href="./order.html" class="identifier">order</a>&lt;s,k&gt;::type</span></tt></td>
  62 <td><a class="reference internal" href="./integral-constant.html">Integral Constant</a> or <tt class="literal"><span class="pre"><a href="./void.html" class="identifier">void_</a></span></tt></td>
  63 <td>Amortized constant time</td>
  64 </tr>
  65 <tr><td><tt class="literal"><span class="pre"><a href="./at.html" class="identifier">at</a>&lt;s,k&gt;::type</span></tt></td>
  66 <td>Any type</td>
  67 <td>Amortized constant time</td>
  68 </tr>
  69 <tr><td><tt class="literal"><span class="pre"><a href="./at.html" class="identifier">at</a>&lt;s,k,def&gt;::type</span></tt></td>
  70 <td>Any type</td>
  71 <td>Amortized constant time</td>
  72 </tr>
  73 <tr><td><tt class="literal"><span class="pre"><a href="./key-type.html" class="identifier">key_type</a>&lt;s,x&gt;::type</span></tt></td>
  74 <td>Any type</td>
  75 <td>Amortized constant time</td>
  76 </tr>
  77 <tr><td><tt class="literal"><span class="pre"><a href="./value-type.html" class="identifier">value_type</a>&lt;s,x&gt;::type</span></tt></td>
  78 <td>Any type</td>
  79 <td>Amortized constant time</td>
  80 </tr>
  81 </tbody>
  82 </table>
  83 </div>
  84 <div class="section" id="id32">
  85 <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
  86 <p>The semantics of an expression are defined only
  87 where they differ from, or are not defined in <a class="reference internal" href="./forward-sequence.html">Forward Sequence</a>.</p>
  88 <table border="1" class="docutils table">
  89 <colgroup>
  90 <col width="33%" />
  91 <col width="67%" />
  92 </colgroup>
  93 <thead valign="bottom">
  94 <tr><th class="head">Expression</th>
  95 <th class="head">Semantics</th>
  96 </tr>
  97 </thead>
  98 <tbody valign="top">
  99 <tr><td><tt class="literal"><span class="pre"><a href="./has-key.html" class="identifier">has_key</a>&lt;s,k&gt;::type</span></tt></td>
 100 <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
 101 <tt class="literal"><span class="pre">c::value</span> <span class="pre">==</span> <span class="pre">true</span></tt> if and only if there is one or more
 102 elements with the key <tt class="literal"><span class="pre">k</span></tt> in <tt class="literal"><span class="pre">s</span></tt>; see <a class="reference internal" href="./has-key.html">has_key</a>.</td>
 103 </tr>
 104 <tr><td><tt class="literal"><span class="pre"><a href="./count.html" class="identifier">count</a>&lt;s,k&gt;::type</span></tt></td>
 105 <td>The number of elements with the key <tt class="literal"><span class="pre">k</span></tt> in <tt class="literal"><span class="pre">s</span></tt>;
 106 see <a class="reference internal" href="./count.html">count</a>.</td>
 107 </tr>
 108 <tr><td><tt class="literal"><span class="pre"><a href="./order.html" class="identifier">order</a>&lt;s,k&gt;::type</span></tt></td>
 109 <td>A unique unsigned <a class="reference internal" href="./integral-constant.html">Integral Constant</a> associated
 110 with the key <tt class="literal"><span class="pre">k</span></tt> in the sequence <tt class="literal"><span class="pre">s</span></tt>; see <a class="reference internal" href="./order.html">order</a>.</td>
 111 </tr>
 112 <tr><td><pre class="first last literal-block">
 113 <a href="./at.html" class="identifier">at</a>&lt;s,k&gt;::type
 114 <a href="./at.html" class="identifier">at</a>&lt;s,k,def&gt;::type
 115 </pre>
 116 </td>
 117 <td>The first element associated with the key <tt class="literal"><span class="pre">k</span></tt>
 118 in the sequence <tt class="literal"><span class="pre">s</span></tt>; see <a class="reference internal" href="./at.html">at</a>.</td>
 119 </tr>
 120 <tr><td><tt class="literal"><span class="pre"><a href="./key-type.html" class="identifier">key_type</a>&lt;s,x&gt;::type</span></tt></td>
 121 <td>The key part of the element <tt class="literal"><span class="pre">x</span></tt> that would be
 122 used to identify <tt class="literal"><span class="pre">x</span></tt> in <tt class="literal"><span class="pre">s</span></tt>; see <a class="reference internal" href="./key-type.html">key_type</a>.</td>
 123 </tr>
 124 <tr><td><tt class="literal"><span class="pre"><a href="./value-type.html" class="identifier">value_type</a>&lt;s,x&gt;::type</span></tt></td>
 125 <td>The value part of the element <tt class="literal"><span class="pre">x</span></tt> that would be
 126 used for <tt class="literal"><span class="pre">x</span></tt> in <tt class="literal"><span class="pre">s</span></tt>; see <a class="reference internal" href="./value-type.html">value_type</a>.</td>
 127 </tr>
 128 </tbody>
 129 </table>
 130 <!-- Invariants
 131 - - - - - - - - - -
 132
 133 For any associative sequence ``s`` the following invariants always hold:
 134
 135  * ??? -->
 136 </div>
 137 <div class="section" id="id33">
 138 <h3><a class="subsection-title" href="#models" name="models">Models</a></h3>
 139 <ul class="simple">
 140 <li><a class="reference internal" href="./set.html">set</a></li>
 141 <li><a class="reference internal" href="./map.html">map</a></li>
 142 </ul>
 143 <!-- * |multiset| -->
 144 </div>
 145 <div class="section" id="id34">
 146 <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
 147 <p><a class="reference internal" href="./sequences.html">Sequences</a>, <a class="reference internal" href="./extensible-associative-sequence.html">Extensible Associative Sequence</a>, <a class="reference internal" href="./has-key.html">has_key</a>, <a class="reference internal" href="./count.html">count</a>, <a class="reference internal" href="./order.html">order</a>, <a class="reference internal" href="./at.html">at</a>, <a class="reference internal" href="./key-type.html">key_type</a>, <a class="reference internal" href="./value-type.html">value_type</a></p>
 148 <!-- Sequences/Concepts//Extensible Associative Sequence |80 -->
 149 </div>
 150 </div>
 151
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