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- <title>The MPL Reference Manual: Associative Sequence</title>
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- <div class="section" id="associative-sequence">
- <h1><a class="toc-backref" href="./concepts.html#id1401">Associative Sequence</a></h1>
- <div class="section" id="id29">
- <h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
- <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
- elements based on keys. Unlike associative containers in the C++ Standard Library,
- MPL associative sequences have no associated ordering relation. Instead,
- <em>type identity</em> is used to impose an equivalence relation on keys, and the
- order in which sequence elements are traversed during iteration is left
- unspecified.</p>
- </div>
- <div class="section" id="id30">
- <h3><a class="subsection-title" href="#definitions" name="definitions">Definitions</a></h3>
- <ul class="simple" id="value-part">
- <span id="key-part"></span><li>A <em>key</em> is a part of the element type used to identify and retrieve
- the element within the sequence.</li>
- <li>A <em>value</em> is a part of the element type retrievied from the sequence
- by its key.</li>
- </ul>
- </div>
- <div class="section" id="id31">
- <h3><a class="subsection-title" href="#expression-requirements" name="expression-requirements">Expression requirements</a></h3>
- <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>,
- <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>
- <p>In addition to the requirements defined in <a class="reference internal" href="./forward-sequence.html">Forward Sequence</a>,
- the following must be met:</p>
- <table border="1" class="docutils table">
- <colgroup>
- <col width="33%" />
- <col width="38%" />
- <col width="29%" />
- </colgroup>
- <thead valign="bottom">
- <tr><th class="head">Expression</th>
- <th class="head">Type</th>
- <th class="head">Complexity</th>
- </tr>
- </thead>
- <tbody valign="top">
- <tr><td><tt class="literal"><span class="pre"><a href="./has-key.html" class="identifier">has_key</a><s,k>::type</span></tt></td>
- <td>Boolean <a class="reference internal" href="./integral-constant.html">Integral Constant</a></td>
- <td>Amortized constant time</td>
- </tr>
- <tr><td><tt class="literal"><span class="pre"><a href="./count.html" class="identifier">count</a><s,k>::type</span></tt></td>
- <td><a class="reference internal" href="./integral-constant.html">Integral Constant</a></td>
- <td>Amortized constant time</td>
- </tr>
- <tr><td><tt class="literal"><span class="pre"><a href="./order.html" class="identifier">order</a><s,k>::type</span></tt></td>
- <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>
- <td>Amortized constant time</td>
- </tr>
- <tr><td><tt class="literal"><span class="pre"><a href="./at.html" class="identifier">at</a><s,k>::type</span></tt></td>
- <td>Any type</td>
- <td>Amortized constant time</td>
- </tr>
- <tr><td><tt class="literal"><span class="pre"><a href="./at.html" class="identifier">at</a><s,k,def>::type</span></tt></td>
- <td>Any type</td>
- <td>Amortized constant time</td>
- </tr>
- <tr><td><tt class="literal"><span class="pre"><a href="./key-type.html" class="identifier">key_type</a><s,x>::type</span></tt></td>
- <td>Any type</td>
- <td>Amortized constant time</td>
- </tr>
- <tr><td><tt class="literal"><span class="pre"><a href="./value-type.html" class="identifier">value_type</a><s,x>::type</span></tt></td>
- <td>Any type</td>
- <td>Amortized constant time</td>
- </tr>
- </tbody>
- </table>
- </div>
- <div class="section" id="id32">
- <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
- <p>The semantics of an expression are defined only
- where they differ from, or are not defined in <a class="reference internal" href="./forward-sequence.html">Forward Sequence</a>.</p>
- <table border="1" class="docutils table">
- <colgroup>
- <col width="33%" />
- <col width="67%" />
- </colgroup>
- <thead valign="bottom">
- <tr><th class="head">Expression</th>
- <th class="head">Semantics</th>
- </tr>
- </thead>
- <tbody valign="top">
- <tr><td><tt class="literal"><span class="pre"><a href="./has-key.html" class="identifier">has_key</a><s,k>::type</span></tt></td>
- <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
- <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
- 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>
- </tr>
- <tr><td><tt class="literal"><span class="pre"><a href="./count.html" class="identifier">count</a><s,k>::type</span></tt></td>
- <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>;
- see <a class="reference internal" href="./count.html">count</a>.</td>
- </tr>
- <tr><td><tt class="literal"><span class="pre"><a href="./order.html" class="identifier">order</a><s,k>::type</span></tt></td>
- <td>A unique unsigned <a class="reference internal" href="./integral-constant.html">Integral Constant</a> associated
- 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>
- </tr>
- <tr><td><pre class="first last literal-block">
- <a href="./at.html" class="identifier">at</a><s,k>::type
- <a href="./at.html" class="identifier">at</a><s,k,def>::type
- </pre>
- </td>
- <td>The first element associated 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="./at.html">at</a>.</td>
- </tr>
- <tr><td><tt class="literal"><span class="pre"><a href="./key-type.html" class="identifier">key_type</a><s,x>::type</span></tt></td>
- <td>The key part of the element <tt class="literal"><span class="pre">x</span></tt> that would be
- 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>
- </tr>
- <tr><td><tt class="literal"><span class="pre"><a href="./value-type.html" class="identifier">value_type</a><s,x>::type</span></tt></td>
- <td>The value part of the element <tt class="literal"><span class="pre">x</span></tt> that would be
- 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>
- </tr>
- </tbody>
- </table>
- <!-- Invariants
- - - - - - - - - - -
- For any associative sequence ``s`` the following invariants always hold:
- * ??? -->
- </div>
- <div class="section" id="id33">
- <h3><a class="subsection-title" href="#models" name="models">Models</a></h3>
- <ul class="simple">
- <li><a class="reference internal" href="./set.html">set</a></li>
- <li><a class="reference internal" href="./map.html">map</a></li>
- </ul>
- <!-- * |multiset| -->
- </div>
- <div class="section" id="id34">
- <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
- <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>
- <!-- Sequences/Concepts//Extensible Associative Sequence |80 -->
- </div>
- </div>
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- <td><div class="copyright-footer"><div class="copyright">Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams</div>
- Distributed under the Boost Software License, Version 1.0. (See accompanying
- file LICENSE_1_0.txt or copy at <a class="reference external" href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)</div></td></tr></table></body>
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