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| <div class="refentry"> |
| <a name="RandomAccessIterator"></a><div class="titlepage"></div> |
| <div class="refnamediv"> |
| <h2><span class="refentrytitle">Concept RandomAccessIterator</span></h2> |
| <p>RandomAccessIterator</p> |
| </div> |
| <div class="refsect1"> |
| <a name="id1022365"></a><h2>Description</h2> |
| <p>A random access iterator is an iterator that can read through |
| a sequence of values. It can move in either direction through the |
| sequence (by any amount in constant time), and can be either mutable |
| (data pointed to by it can be changed) or not mutable.</p> |
| <p>An iterator represents a position in a sequence. Therefore, |
| the iterator can point into the sequence (returning a value when |
| dereferenced and being incrementable), or be off-the-end (and not |
| dereferenceable or incrementable).</p> |
| </div> |
| <div class="refsect1"> |
| <a name="id1022385"></a><h2>Refinement of</h2> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"><p><a class="link" href="BidirectionalIterator.html" title="Concept BidirectionalIterator">BidirectionalIterator</a></p></li> |
| <li class="listitem"><p><a class="link" href="LessThanComparable.html" title="Concept LessThanComparable">LessThanComparable</a></p></li> |
| </ul></div> |
| </div> |
| <div class="refsect1"> |
| <a name="id1022406"></a><h2>Associated types</h2> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| <p><span class="bold"><strong>value_type</strong></span></p> |
| <pre class="literallayout">std::iterator_traits<Iter>::value_type</pre> |
| <p>The value type of the iterator</p> |
| </li> |
| <li class="listitem"> |
| <p><span class="bold"><strong>category</strong></span></p> |
| <pre class="literallayout">std::iterator_traits<Iter>::iterator_category</pre> |
| <p>The category of the iterator</p> |
| </li> |
| <li class="listitem"> |
| <p><span class="bold"><strong>difference_type</strong></span></p> |
| <pre class="literallayout">std::iterator_traits<Iter>::difference_type</pre> |
| <p>The difference type of the iterator (measure of the number |
| of steps between two iterators)</p> |
| </li> |
| </ul></div> |
| </div> |
| <div class="refsect1"> |
| <a name="id1022464"></a><h2>Notation</h2> |
| <div class="variablelist"><dl> |
| <dt><span class="term">Iter</span></dt> |
| <dd>A type playing the role of iterator-type in the <a class="link" href="RandomAccessIterator.html" title="Concept RandomAccessIterator">RandomAccessIterator</a> concept.</dd> |
| <dt> |
| <span class="term"><code class="varname">i</code>, </span><span class="term"><code class="varname">j</code></span> |
| </dt> |
| <dd>Objects of type Iter</dd> |
| <dt><span class="term"><code class="varname">x</code></span></dt> |
| <dd>Object of type value_type</dd> |
| <dt><span class="term"><code class="varname">n</code></span></dt> |
| <dd>Object of type difference_type</dd> |
| <dt><span class="term"><code class="varname">int_off</code></span></dt> |
| <dd>Object of type int</dd> |
| </dl></div> |
| </div> |
| <div class="refsect1"> |
| <a name="id1022519"></a><h2>Type expressions</h2> |
| <div class="variablelist"><dl> |
| <dt><span class="term">Category tag</span></dt> |
| <dd><p><span class="type">category</span> must be |
| derived from <span class="type">std::random_access_iterator_tag</span>. |
| </p></dd> |
| </dl></div> |
| </div> |
| <div class="refsect1"> |
| <a name="id1022538"></a><h2>Valid expressions</h2> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th>Name</th> |
| <th>Expression</th> |
| <th>Type</th> |
| <th>Semantics</th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td><p>Motion</p></td> |
| <td><p>i += n</p></td> |
| <td><p><span class="type">Iter &</span></p></td> |
| <td><p>Equivalent to applying <code class="computeroutput">i++</code> <code class="computeroutput">n</code> times |
| if <code class="computeroutput">n</code> is positive, applying <code class="computeroutput">i--</code> |
| <code class="computeroutput">-n</code> times if <code class="computeroutput">n</code> is negative, and to a null |
| operation if <code class="computeroutput">n</code> is zero.</p></td> |
| </tr> |
| <tr> |
| <td><p>Motion (with integer offset)</p></td> |
| <td><p>i += int_off</p></td> |
| <td><p><span class="type">Iter &</span></p></td> |
| <td><p>Equivalent to applying <code class="computeroutput">i++</code> <code class="computeroutput">n</code> times |
| if <code class="computeroutput">n</code> is positive, applying <code class="computeroutput">i--</code> |
| <code class="computeroutput">-n</code> times if <code class="computeroutput">n</code> is negative, and to a null |
| operation if <code class="computeroutput">n</code> is zero.</p></td> |
| </tr> |
| <tr> |
| <td><p>Subtractive motion</p></td> |
| <td><p>i -= n</p></td> |
| <td><p><span class="type">Iter &</span></p></td> |
| <td><p>Equivalent to <code class="computeroutput">i+=(-n)</code></p></td> |
| </tr> |
| <tr> |
| <td><p>Subtractive motion (with integer offset)</p></td> |
| <td><p>i -= int_off</p></td> |
| <td><p><span class="type">Iter &</span></p></td> |
| <td><p>Equivalent to <code class="computeroutput">i+=(-n)</code></p></td> |
| </tr> |
| <tr> |
| <td><p>Addition</p></td> |
| <td><p>i + n</p></td> |
| <td><p><span class="type">Iter</span></p></td> |
| <td><p>Equivalent to <code class="computeroutput">{Iter j = i; j += n; return j;}</code></p></td> |
| </tr> |
| <tr> |
| <td><p>Addition with integer</p></td> |
| <td><p>i + int_off</p></td> |
| <td><p><span class="type">Iter</span></p></td> |
| <td><p>Equivalent to <code class="computeroutput">{Iter j = i; j += n; return j;}</code></p></td> |
| </tr> |
| <tr> |
| <td><p>Addition (count first)</p></td> |
| <td><p>n + i</p></td> |
| <td><p><span class="type">Iter</span></p></td> |
| <td><p>Equivalent to <code class="computeroutput">i + n</code></p></td> |
| </tr> |
| <tr> |
| <td><p>Addition with integer (count first)</p></td> |
| <td><p>int_off + i</p></td> |
| <td><p><span class="type">Iter</span></p></td> |
| <td><p>Equivalent to <code class="computeroutput">i + n</code></p></td> |
| </tr> |
| <tr> |
| <td><p>Subtraction</p></td> |
| <td><p>i - n</p></td> |
| <td><p><span class="type">Iter</span></p></td> |
| <td><p>Equivalent to <code class="computeroutput">i + (-n)</code></p></td> |
| </tr> |
| <tr> |
| <td><p>Subtraction with integer</p></td> |
| <td><p>i - int_off</p></td> |
| <td><p><span class="type">Iter</span></p></td> |
| <td><p>Equivalent to <code class="computeroutput">i + (-n)</code></p></td> |
| </tr> |
| <tr> |
| <td><p>Distance</p></td> |
| <td><p>i - j</p></td> |
| <td><p><span class="type">difference_type</span></p></td> |
| <td><p>The number of times <code class="computeroutput">i</code> must be incremented (or |
| decremented if the result is negative) to reach <code class="computeroutput">j</code>. Not |
| defined if <code class="computeroutput">j</code> is not reachable from |
| <code class="computeroutput">i</code>.</p></td> |
| </tr> |
| <tr> |
| <td><p>Element access</p></td> |
| <td><p>i[n]</p></td> |
| <td><p><span class="type">const-if-not-mutable value_type &</span></p></td> |
| <td><p>Equivalent to <code class="computeroutput">*(i + n)</code></p></td> |
| </tr> |
| <tr> |
| <td><p>Element access with integer index</p></td> |
| <td><p>i[int_off]</p></td> |
| <td><p><span class="type">const-if-not-mutable value_type &</span></p></td> |
| <td><p>Equivalent to <code class="computeroutput">*(i + n)</code></p></td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <div class="refsect1"> |
| <a name="id1022921"></a><h2>Complexity</h2> |
| <p> |
| All iterator operations must take amortized constant time. |
| </p> |
| </div> |
| <div class="refsect1"> |
| <a name="id1022928"></a><h2>Models</h2> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"><span class="simplelist"><span class="type">T *</span></span></li> |
| <li class="listitem"><span class="simplelist"><span class="type">std::vector<T>::iterator</span></span></li> |
| <li class="listitem"><span class="simplelist"><span class="type">std::vector<T>::const_iterator</span></span></li> |
| <li class="listitem"><span class="simplelist"><span class="type">std::deque<T>::iterator</span></span></li> |
| <li class="listitem"><span class="simplelist"><span class="type">std::deque<T>::const_iterator</span></span></li> |
| </ul></div> |
| </div> |
| <div class="refsect1"> |
| <a name="id1022974"></a><h2>See also</h2> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><a class="link" href="LessThanComparable.html" title="Concept LessThanComparable">LessThanComparable</a></p></li></ul></div> |
| </div> |
| </div> |
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