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<div class="section" id="random-access-iterator">
<h1><a class="toc-backref" href="./iterators-concepts.html#id1452">Random Access Iterator</a></h1>
<div class="section" id="id397">
<h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
<p>A <a class="reference internal" href="./random-access-iterator.html">Random Access Iterator</a> is a <a class="reference internal" href="./bidirectional-iterator.html">Bidirectional Iterator</a> that provides
constant-time guarantees on moving the iterator an arbitrary number of positions
forward or backward and for measuring the distance to another iterator in the
same sequence.</p>
</div>
<div class="section" id="id398">
<h3><a class="subsection-title" href="#refinement-of" name="refinement-of">Refinement of</a></h3>
<p><a class="reference internal" href="./bidirectional-iterator.html">Bidirectional Iterator</a></p>
</div>
<div class="section" id="id399">
<h3><a class="subsection-title" href="#expression-requirements" name="expression-requirements">Expression requirements</a></h3>
<p>In addition to the requirements defined in <a class="reference internal" href="./bidirectional-iterator.html">Bidirectional Iterator</a>,
the following requirements must be met.</p>
<table border="1" class="docutils table">
<colgroup>
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<col width="44%" />
<col width="28%" />
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<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="./next.html" class="identifier">next</a>&lt;i&gt;::type</span></tt></td>
<td><a class="reference internal" href="./random-access-iterator.html">Random Access Iterator</a></td>
<td>Amortized constant time</td>
</tr>
<tr><td><tt class="literal"><span class="pre"><a href="./prior.html" class="identifier">prior</a>&lt;i&gt;::type</span></tt></td>
<td><a class="reference internal" href="./random-access-iterator.html">Random Access Iterator</a></td>
<td>Amortized constant time</td>
</tr>
<tr><td><tt class="literal"><span class="pre">i::category</span></tt></td>
<td><a class="reference internal" href="./integral-constant.html">Integral Constant</a>, convertible
to <tt class="literal"><span class="pre">random_access_iterator_tag</span></tt></td>
<td>Constant time</td>
</tr>
<tr><td><tt class="literal"><span class="pre"><a href="./advance.html" class="identifier">advance</a>&lt;i,n&gt;::type</span></tt></td>
<td><a class="reference internal" href="./random-access-iterator.html">Random Access Iterator</a></td>
<td>Amortized constant time</td>
</tr>
<tr><td><tt class="literal"><span class="pre"><a href="./distance.html" class="identifier">distance</a>&lt;i,j&gt;::type</span></tt></td>
<td><a class="reference internal" href="./integral-constant.html">Integral Constant</a></td>
<td>Amortized constant time</td>
</tr>
</tbody>
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<div class="section" id="id400">
<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
<pre class="literal-block">
typedef <a href="./advance.html" class="identifier">advance</a>&lt;i,n&gt;::type j;
</pre>
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<tr class="field"><th class="field-name">Semantics:</th><td class="field-body">See <tt class="literal"><span class="pre"><a href="./advance.html" class="identifier">advance</a></span></tt> specification</td>
</tr>
</tbody>
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<pre class="literal-block">
typedef <a href="./distance.html" class="identifier">distance</a>&lt;i,j&gt;::type n;
</pre>
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<tr class="field"><th class="field-name">Semantics:</th><td class="field-body">See <tt class="literal"><span class="pre"><a href="./distance.html" class="identifier">distance</a></span></tt> specification</td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="id401">
<h3><a class="subsection-title" href="#invariants" name="invariants">Invariants</a></h3>
<p>For any random access iterators <tt class="literal"><span class="pre">i</span></tt> and <tt class="literal"><span class="pre">j</span></tt> the following invariants always
hold:</p>
<ul class="simple">
<li>If <tt class="literal"><span class="pre"><a href="./advance.html" class="identifier">advance</a>&lt;i,n&gt;::type</span></tt> is well-defined, then
<tt class="literal"><span class="pre"><a href="./advance.html" class="identifier">advance</a>&lt;</span> <span class="pre"><a href="./advance.html" class="identifier">advance</a>&lt;i,n&gt;::type,</span> <span class="pre"><a href="./negate.html" class="identifier">negate</a>&lt;n&gt;::type</span> <span class="pre">&gt;::type</span></tt> is a null operation.</li>
</ul>
</div>
<div class="section" id="id402">
<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
<p><a class="reference internal" href="./iterators.html">Iterators</a>, <a class="reference internal" href="./bidirectional-iterator.html">Bidirectional Iterator</a>, <a class="reference internal" href="./random-access-sequence.html">Random Access Sequence</a>, <a class="reference internal" href="./advance.html">advance</a>, <a class="reference internal" href="./distance.html">distance</a></p>
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