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<title>Random
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Access Sequence</title>
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<a accesskey="p" href="bidirectional_sequence.html"><img src="../../../images/prev.png" alt="Prev"></a><a accesskey="u" href="../concepts.html"><img src="../../../images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../images/home.png" alt="Home"></a><a accesskey="n" href="associative_sequence.html"><img src="../../../images/next.png" alt="Next"></a>
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<div class="section" lang="en">
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<div class="titlepage"><div><div><h4 class="title">
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<a name="fusion.sequences.concepts.random_access_sequence"></a><a href="random_access_sequence.html" title="Random
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Access Sequence">Random
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Access Sequence</a></h4></div></div></div>
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<a name="fusion.sequences.concepts.random_access_sequence.description"></a><h5>
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<a name="id474531"></a>
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<a href="random_access_sequence.html#fusion.sequences.concepts.random_access_sequence.description">Description</a>
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</h5>
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<p>
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A Random Access Sequence is a <a href="bidirectional_sequence.html" title="Bidirectional
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Sequence">Bidirectional
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Sequence</a> whose iterators model <a href="../../iterators/concepts/random_access_iterator.html" title="Random
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Access Iterator">Random
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Access Iterator</a>. It guarantees constant time access to arbitrary
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sequence elements.
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</p>
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<a name="fusion.sequences.concepts.random_access_sequence.refinement_of"></a><h5>
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<a name="id474583"></a>
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<a href="random_access_sequence.html#fusion.sequences.concepts.random_access_sequence.refinement_of">Refinement
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of</a>
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</h5>
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<p>
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<a href="bidirectional_sequence.html" title="Bidirectional
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Sequence">Bidirectional
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Sequence</a>
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</p>
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<div class="variablelist">
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<p class="title"><b>Notation</b></p>
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<dl>
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<dt><span class="term"><tt class="computeroutput"><span class="identifier">s</span></tt></span></dt>
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<dd>
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A Random Access Sequence
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</dd>
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<dt><span class="term"><tt class="computeroutput"><span class="identifier">S</span></tt></span></dt>
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<dd>
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A Random Access Sequence type
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</dd>
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<dt><span class="term"><tt class="computeroutput"><span class="identifier">N</span></tt></span></dt>
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<dd>
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An integral constant
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</dd>
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<dt><span class="term"><tt class="computeroutput"><span class="identifier">o</span></tt></span></dt>
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<dd>
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An arbitrary object
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</dd>
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<dt><span class="term"><tt class="computeroutput"><span class="identifier">e</span></tt></span></dt>
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<dd>
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A Sequence element
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</dd>
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</dl>
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</div>
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<a name="fusion.sequences.concepts.random_access_sequence.valid_expressions"></a><h5>
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<a name="id474719"></a>
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<a href="random_access_sequence.html#fusion.sequences.concepts.random_access_sequence.valid_expressions">Valid
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Expressions</a>
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</h5>
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<p>
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In addition to the requirements defined in <a href="bidirectional_sequence.html" title="Bidirectional
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Sequence">Bidirectional
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Sequence</a>, for any Random Access Sequence the following must be met:
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</p>
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<div class="informaltable">
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<h4>
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<a name="id474757"></a>
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</h4>
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<table class="table">
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<colgroup>
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<col>
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<col>
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<col>
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<col>
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</colgroup>
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<thead><tr>
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<th>Expression</th>
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<th>Return type</th>
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<th>Type Requirements</th>
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<th>Runtime
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Complexity</th>
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</tr></thead>
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<tbody>
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<tr>
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<td><tt class="computeroutput"><a href="../intrinsics/functions/begin.html" title="begin"><tt class="computeroutput"><span class="identifier">begin</span></tt></a><span class="special">(</span><span class="identifier">s</span><span class="special">)</span></tt></td>
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<td><a href="../../iterators/concepts/random_access_iterator.html" title="Random
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Access Iterator">Random
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Access Iterator</a></td>
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<td> </td>
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<td>Constant</td>
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</tr>
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<tr>
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<td><tt class="computeroutput"><a href="../intrinsics/functions/end.html" title="end"><tt class="computeroutput"><span class="identifier">end</span></tt></a><span class="special">(</span><span class="identifier">s</span><span class="special">)</span></tt></td>
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<td><a href="../../iterators/concepts/random_access_iterator.html" title="Random
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Access Iterator">Random
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Access Iterator</a></td>
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<td> </td>
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<td>Constant</td>
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</tr>
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<tr>
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<td><tt class="computeroutput"><a href="../intrinsics/functions/at.html" title="at"><tt class="computeroutput"><span class="identifier">at</span></tt></a><span class="special"><</span><span class="identifier">N</span><span class="special">>(</span><span class="identifier">s</span><span class="special">)</span></tt></td>
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<td>Any
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type</td>
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<td> </td>
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<td>Constant</td>
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</tr>
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<tr>
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<td><tt class="computeroutput"><a href="../intrinsics/functions/at.html" title="at"><tt class="computeroutput"><span class="identifier">at</span></tt></a><span class="special"><</span><span class="identifier">N</span><span class="special">>(</span><span class="identifier">s</span><span class="special">)</span> <span class="special">=</span> <span class="identifier">o</span></tt></td>
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<td>Any
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type</td>
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<td>
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<tt class="computeroutput"><span class="identifier">s</span></tt>
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is mutable and <tt class="computeroutput"><span class="identifier">e</span> <span class="special">=</span> <span class="identifier">o</span></tt>,
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where <tt class="computeroutput"><span class="identifier">e</span></tt> is the first
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element in the sequence, is a valid expression.</td>
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<td>Constant</td>
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</tr>
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</tbody>
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</table>
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</div>
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<a name="fusion.sequences.concepts.random_access_sequence.result_type_expressions"></a><h5>
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<a name="id475083"></a>
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<a href="random_access_sequence.html#fusion.sequences.concepts.random_access_sequence.result_type_expressions">Result
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Type Expressions</a>
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</h5>
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<div class="informaltable">
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<h4>
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<a name="id475106"></a>
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</h4>
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<table class="table">
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<colgroup>
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<col>
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<col>
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</colgroup>
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<thead><tr>
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<th>Expression</th>
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<th>Compile Time Complexity</th>
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</tr></thead>
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<tbody>
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<tr>
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<td><tt class="computeroutput"><a href="../intrinsics/metafunctions/begin.html" title="begin"><tt class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">begin</span></tt></a><span class="special"><</span><span class="identifier">S</span><span class="special">>::</span><span class="identifier">type</span></tt></td>
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<td>Amortized constant
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time</td>
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</tr>
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<tr>
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<td><tt class="computeroutput"><a href="../intrinsics/metafunctions/end.html" title="end"><tt class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">end</span></tt></a><span class="special"><</span><span class="identifier">S</span><span class="special">>::</span><span class="identifier">type</span></tt></td>
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<td>Amortized constant
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time</td>
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</tr>
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<tr>
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<td><tt class="computeroutput"><a href="../intrinsics/metafunctions/at.html" title="at"><tt class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">at</span></tt></a><span class="special"><</span><span class="identifier">S</span><span class="special">,</span> <span class="identifier">N</span><span class="special">>::</span><span class="identifier">type</span></tt></td>
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<td>Amortized constant
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time</td>
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</tr>
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<tr>
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<td><tt class="computeroutput"><a href="../intrinsics/metafunctions/value_at.html" title="value_at"><tt class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">value_at</span></tt></a><span class="special"><</span><span class="identifier">S</span><span class="special">,</span> <span class="identifier">N</span><span class="special">>::</span><span class="identifier">type</span></tt></td>
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<td>Amortized constant
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time</td>
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</tr>
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</tbody>
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</table>
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</div>
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<p class="blurb">
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<span class="inlinemediaobject"><img src="../../../images/note.png" alt="note"></span> <tt class="computeroutput"><a href="../intrinsics/metafunctions/at.html" title="at"><tt class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">at</span></tt></a><span class="special"><</span><span class="identifier">S</span><span class="special">,</span> <span class="identifier">N</span><span class="special">></span></tt>
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returns the actual type returned by <tt class="computeroutput"><a href="../intrinsics/functions/at.html" title="at"><tt class="computeroutput"><span class="identifier">at</span></tt></a><span class="special"><</span><span class="identifier">N</span><span class="special">>(</span><span class="identifier">s</span><span class="special">)</span></tt>. In
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most cases, this is a reference. Hence, there is no way to know the exact
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element type using <tt class="computeroutput"><a href="../intrinsics/metafunctions/at.html" title="at"><tt class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">at</span></tt></a><span class="special"><</span><span class="identifier">S</span><span class="special">,</span> <span class="identifier">N</span><span class="special">></span></tt>.The
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element at <tt class="computeroutput"><span class="identifier">N</span></tt> may actually
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be a reference to begin with. For this purpose, you can use <tt class="computeroutput"><a href="../intrinsics/metafunctions/value_at.html" title="value_at"><tt class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">value_at</span></tt></a><span class="special"><</span><span class="identifier">S</span><span class="special">,</span> <span class="identifier">N</span><span class="special">></span></tt>.
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</p>
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<a name="fusion.sequences.concepts.random_access_sequence.expression_semantics"></a><h5>
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<a name="id475657"></a>
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<a href="random_access_sequence.html#fusion.sequences.concepts.random_access_sequence.expression_semantics">Expression
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Semantics</a>
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</h5>
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<p>
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The semantics of an expression are defined only where they differ from,
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or are not defined in <a href="bidirectional_sequence.html" title="Bidirectional
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Sequence">Bidirectional
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Sequence</a>.
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</p>
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<div class="informaltable">
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<h4>
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<a name="id475696"></a>
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</h4>
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<table class="table">
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<colgroup>
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<col>
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<col>
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</colgroup>
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<thead><tr>
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<th>Expression</th>
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<th>Semantics</th>
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</tr></thead>
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<tbody><tr>
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<td><tt class="computeroutput"><a href="../intrinsics/functions/at.html" title="at"><tt class="computeroutput"><span class="identifier">at</span></tt></a><span class="special"><</span><span class="identifier">N</span><span class="special">>(</span><span class="identifier">s</span><span class="special">)</span></tt></td>
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<td>The
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Nth element from the beginning of the sequence; see <a href="../intrinsics/functions/at.html" title="at"><tt class="computeroutput"><span class="identifier">at</span></tt></a>.</td>
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</tr></tbody>
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</table>
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</div>
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<a name="fusion.sequences.concepts.random_access_sequence.models"></a><h5>
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<a name="id475802"></a>
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<a href="random_access_sequence.html#fusion.sequences.concepts.random_access_sequence.models">Models</a>
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</h5>
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<div class="itemizedlist"><ul type="disc">
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<li><a href="../adapted/std__pair.html" title="std::pair"><tt class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span></tt></a></li>
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<li><a href="../adapted/boost__array.html" title="boost::array"><tt class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">array</span></tt></a></li>
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<li><a href="../containers/vector.html" title="vector"><tt class="computeroutput"><span class="identifier">vector</span></tt></a></li>
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<li>
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<a href="../views/iterator_range.html" title="iterator_range"><tt class="computeroutput"><span class="identifier">iterator_range</span></tt></a>
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(where adapted sequence is a Random Access Sequence)
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</li>
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<li>
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<a href="../views/transform_view.html" title="transform_view"><tt class="computeroutput"><span class="identifier">transform_view</span></tt></a>
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(where adapted sequence is a Random Access Sequence)
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</li>
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<li><a href="../views/reverse_view.html" title="reverse_view"><tt class="computeroutput"><span class="identifier">reverse_view</span></tt></a></li>
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</ul></div>
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</div>
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="left"></td>
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<td align="right"><small>Copyright © 2001-2005 Joel de Guzman, Dan Marsden</small></td>
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</tr></table>
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<hr>
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<div class="spirit-nav">
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<a accesskey="p" href="bidirectional_sequence.html"><img src="../../../images/prev.png" alt="Prev"></a><a accesskey="u" href="../concepts.html"><img src="../../../images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../images/home.png" alt="Home"></a><a accesskey="n" href="associative_sequence.html"><img src="../../../images/next.png" alt="Next"></a>
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