boost_fusion/doc/html/fusion/sequence/concepts/associative_sequence.html

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<div class="section" title="Associative Sequence">
<div class="titlepage"><div><div><h4 class="title">
<a name="fusion.sequence.concepts.associative_sequence"></a><a class="link" href="associative_sequence.html" title="Associative Sequence">Associative
        Sequence</a>
</h4></div></div></div>
<a name="fusion.sequence.concepts.associative_sequence.description"></a><h6>
<a name="id651334"></a>
          <a class="link" href="associative_sequence.html#fusion.sequence.concepts.associative_sequence.description">Description</a>
        </h6>
<p>
          An Associative Sequence allows efficient retrieval of elements based on
          keys. Like associative sequences in <a href="http://www.boost.org/libs/mpl/index.html" target="_top">MPL</a>,
          and unlike associative containers in <a href="http://en.wikipedia.org/wiki/Standard_Template_Library" target="_top">STL</a>,
          Fusion associative sequences have no implied ordering relation. Instead,
          type identity is used to impose an equivalence relation on keys.
        </p>
<div class="variablelist" title="Notation">
<p class="title"><b>Notation</b></p>
<dl>
<dt><span class="term"><code class="computeroutput"><span class="identifier">s</span></code></span></dt>
<dd><p>
              An Associative Sequence
            </p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">S</span></code></span></dt>
<dd><p>
              An Associative Sequence type
            </p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">K</span></code></span></dt>
<dd><p>
              An arbitrary <span class="emphasis"><em>key</em></span> type
            </p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">o</span></code></span></dt>
<dd><p>
              An arbitrary object
            </p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">e</span></code></span></dt>
<dd><p>
              A Sequence element
            </p></dd>
</dl>
</div>
<a name="fusion.sequence.concepts.associative_sequence.valid_expressions"></a><h6>
<a name="id651467"></a>
          <a class="link" href="associative_sequence.html#fusion.sequence.concepts.associative_sequence.valid_expressions">Valid
          Expressions</a>
        </h6>
<p>
          For any Associative Sequence the following expressions must be valid:
        </p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                <p>
                  Expression
                </p>
                </th>
<th>
                <p>
                  Return type
                </p>
                </th>
<th>
                <p>
                  Type Requirements
                </p>
                </th>
<th>
                <p>
                  Runtime Complexity
                </p>
                </th>
</tr></thead>
<tbody>
<tr>
<td>
                <p>
                  <code class="computeroutput"><a class="link" href="../intrinsic/functions/has_key.html" title="has_key"><code class="computeroutput"><span class="identifier">has_key</span></code></a><span class="special">&lt;</span><span class="identifier">K</span><span class="special">&gt;(</span><span class="identifier">s</span><span class="special">)</span></code>
                </p>
                </td>
<td>
                <p>
                  <a href="http://www.boost.org/libs/mpl/doc/refmanual/integral-constant.html" target="_top">MPL
                  Boolean Constant</a>. Convertible to bool.
                </p>
                </td>
<td>
                <p>
                </p>
                </td>
<td>
                <p>
                  Constant
                </p>
                </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput"><a class="link" href="../intrinsic/functions/at_key.html" title="at_key"><code class="computeroutput"><span class="identifier">at_key</span></code></a><span class="special">&lt;</span><span class="identifier">K</span><span class="special">&gt;(</span><span class="identifier">s</span><span class="special">)</span></code>
                </p>
                </td>
<td>
                <p>
                  Any type
                </p>
                </td>
<td>
                <p>
                </p>
                </td>
<td>
                <p>
                  Constant
                </p>
                </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput"><a class="link" href="../intrinsic/functions/at_key.html" title="at_key"><code class="computeroutput"><span class="identifier">at_key</span></code></a><span class="special">&lt;</span><span class="identifier">K</span><span class="special">&gt;(</span><span class="identifier">s</span><span class="special">)</span>
                  <span class="special">=</span> <span class="identifier">o</span></code>
                </p>
                </td>
<td>
                <p>
                  Any type
                </p>
                </td>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">s</span></code> is mutable and
                  <code class="computeroutput"><span class="identifier">e</span> <span class="special">=</span>
                  <span class="identifier">o</span></code>, where <code class="computeroutput"><span class="identifier">e</span></code> is the first element in the
                  sequence, is a valid expression.
                </p>
                </td>
<td>
                <p>
                  Constant
                </p>
                </td>
</tr>
</tbody>
</table></div>
<a name="fusion.sequence.concepts.associative_sequence.result_type_expressions"></a><h6>
<a name="id651754"></a>
          <a class="link" href="associative_sequence.html#fusion.sequence.concepts.associative_sequence.result_type_expressions">Result
          Type Expressions</a>
        </h6>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                <p>
                  Expression
                </p>
                </th>
<th>
                <p>
                  Compile Time Complexity
                </p>
                </th>
</tr></thead>
<tbody>
<tr>
<td>
                <p>
                  <code class="computeroutput"><a class="link" href="../intrinsic/metafunctions/has_key.html" title="has_key"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">has_key</span></code></a><span class="special">&lt;</span><span class="identifier">S</span><span class="special">,</span>
                  <span class="identifier">K</span><span class="special">&gt;::</span><span class="identifier">type</span></code>
                </p>
                </td>
<td>
                <p>
                  Amortized constant time
                </p>
                </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput"><a class="link" href="../intrinsic/metafunctions/at_key.html" title="at_key"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">at_key</span></code></a><span class="special">&lt;</span><span class="identifier">S</span><span class="special">,</span>
                  <span class="identifier">K</span><span class="special">&gt;::</span><span class="identifier">type</span></code>
                </p>
                </td>
<td>
                <p>
                  Amortized constant time
                </p>
                </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput"><a class="link" href="../intrinsic/metafunctions/value_at_key.html" title="value_at_key"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">value_at_key</span></code></a><span class="special">&lt;</span><span class="identifier">S</span><span class="special">,</span>
                  <span class="identifier">K</span><span class="special">&gt;::</span><span class="identifier">type</span></code>
                </p>
                </td>
<td>
                <p>
                  Amortized constant time
                </p>
                </td>
</tr>
</tbody>
</table></div>
<div class="sidebar">
<p class="title"><b></b></p>
<p>
          <span class="inlinemediaobject"><img src="../../../images/note.png" alt="note"></span> <code class="computeroutput"><a class="link" href="../intrinsic/metafunctions/at_key.html" title="at_key"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">at_key</span></code></a><span class="special">&lt;</span><span class="identifier">S</span><span class="special">,</span> <span class="identifier">K</span><span class="special">&gt;</span></code> returns the actual type returned by
          <code class="computeroutput"><a class="link" href="../intrinsic/functions/at_key.html" title="at_key"><code class="computeroutput"><span class="identifier">at_key</span></code></a><span class="special">&lt;</span><span class="identifier">K</span><span class="special">&gt;(</span><span class="identifier">s</span><span class="special">)</span></code>. In
          most cases, this is a reference. Hence, there is no way to know the exact
          element type using <code class="computeroutput"><a class="link" href="../intrinsic/metafunctions/at_key.html" title="at_key"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">at_key</span></code></a><span class="special">&lt;</span><span class="identifier">S</span><span class="special">,</span> <span class="identifier">K</span><span class="special">&gt;</span></code>.The element at <code class="computeroutput"><span class="identifier">K</span></code>
          may actually be a reference to begin with. For this purpose, you can use
          <code class="computeroutput"><a class="link" href="../intrinsic/metafunctions/value_at_key.html" title="value_at_key"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">value_at_key</span></code></a><span class="special">&lt;</span><span class="identifier">S</span><span class="special">,</span> <span class="identifier">N</span><span class="special">&gt;</span></code>.
        </p>
</div>
<a name="fusion.sequence.concepts.associative_sequence.expression_semantics"></a><h6>
<a name="id652157"></a>
          <a class="link" href="associative_sequence.html#fusion.sequence.concepts.associative_sequence.expression_semantics">Expression
          Semantics</a>
        </h6>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                <p>
                  Expression
                </p>
                </th>
<th>
                <p>
                  Semantics
                </p>
                </th>
</tr></thead>
<tbody>
<tr>
<td>
                <p>
                  <code class="computeroutput"><a class="link" href="../intrinsic/functions/has_key.html" title="has_key"><code class="computeroutput"><span class="identifier">has_key</span></code></a><span class="special">&lt;</span><span class="identifier">K</span><span class="special">&gt;(</span><span class="identifier">s</span><span class="special">)</span></code>
                </p>
                </td>
<td>
                <p>
                  A boolean Integral Constant <code class="computeroutput"><span class="identifier">c</span></code>
                  such that <code class="computeroutput"><span class="identifier">c</span><span class="special">::</span><span class="identifier">value</span> <span class="special">==</span>
                  <span class="keyword">true</span></code> if and only if there
                  is one or more elements with the key <code class="computeroutput"><span class="identifier">k</span></code>
                  in <code class="computeroutput"><span class="identifier">s</span></code>; see <a class="link" href="../intrinsic/functions/has_key.html" title="has_key"><code class="computeroutput"><span class="identifier">has_key</span></code></a>.
                </p>
                </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput"><a class="link" href="../intrinsic/functions/at_key.html" title="at_key"><code class="computeroutput"><span class="identifier">at_key</span></code></a><span class="special">&lt;</span><span class="identifier">K</span><span class="special">&gt;(</span><span class="identifier">s</span><span class="special">)</span></code>
                </p>
                </td>
<td>
                <p>
                  The element associated with the key <code class="computeroutput"><span class="identifier">K</span></code>
                  in the sequence <code class="computeroutput"><span class="identifier">s</span></code>;
                  see <a class="link" href="../intrinsic/functions/at.html" title="at"><code class="computeroutput"><span class="identifier">at</span></code></a>.
                </p>
                </td>
</tr>
</tbody>
</table></div>
<a name="fusion.sequence.concepts.associative_sequence.models"></a><h6>
<a name="id653538"></a>
          <a class="link" href="associative_sequence.html#fusion.sequence.concepts.associative_sequence.models">Models</a>
        </h6>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem"><a class="link" href="../../container/set.html" title="set"><code class="computeroutput"><span class="identifier">set</span></code></a></li>
<li class="listitem"><a class="link" href="../../container/map.html" title="map"><code class="computeroutput"><span class="identifier">map</span></code></a></li>
<li class="listitem">
<a class="link" href="../../view/filter_view.html" title="filter_view"><code class="computeroutput"><span class="identifier">filter_view</span></code></a>
            (where adapted sequence is an <a class="link" href="associative_sequence.html" title="Associative Sequence">Associative
            Sequence</a> and a <a class="link" href="forward_sequence.html" title="Forward Sequence">Forward
            Sequence</a>)
          </li>
<li class="listitem">
<a class="link" href="../../view/iterator_range.html" title="iterator_range"><code class="computeroutput"><span class="identifier">iterator_range</span></code></a>
            (where adapted iterators are <a class="link" href="../../iterator/concepts/associative_iterator.html" title="Associative Iterator">Associative
            Iterator</a>s)
          </li>
<li class="listitem">
<a class="link" href="../../view/joint_view.html" title="joint_view"><code class="computeroutput"><span class="identifier">joint_view</span></code></a>
            (where adapted sequences are <a class="link" href="associative_sequence.html" title="Associative Sequence">Associative
            Sequence</a>s and <a class="link" href="forward_sequence.html" title="Forward Sequence">Forward
            Sequence</a>s)
          </li>
<li class="listitem">
<a class="link" href="../../view/reverse_view.html" title="reverse_view"><code class="computeroutput"><span class="identifier">reverse_view</span></code></a>
            (where adapted sequence is an <a class="link" href="associative_sequence.html" title="Associative Sequence">Associative
            Sequence</a> and a <a class="link" href="bidirectional_sequence.html" title="Bidirectional Sequence">Bidirectional
            Sequence</a>)
          </li>
</ul></div>
</div>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2001-2007 Joel de Guzman, Dan Marsden, Tobias
      Schwinger<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        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>)
      </p>
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