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| <h2><span class="refentrytitle">Concept ForwardIterator</span></h2> |
| <p>ForwardIterator</p> |
| </div> |
| <div class="refsect1"> |
| <a name="id1021661"></a><h2>Description</h2> |
| <p>A forward iterator is an iterator that can read through a sequence of |
| values. It is multi-pass (old values of the iterator can be |
| re-used), 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="id1021680"></a><h2>Refinement of</h2> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"><p><a class="link" href="InputIterator.html" title="Concept InputIterator">InputIterator</a></p></li> |
| <li class="listitem"><p><a class="link" href="OutputIterator.html" title="Concept OutputIterator">OutputIterator</a></p></li> |
| </ul></div> |
| </div> |
| <div class="refsect1"> |
| <a name="id1021700"></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> |
| </ul></div> |
| </div> |
| <div class="refsect1"> |
| <a name="id1021740"></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="ForwardIterator.html" title="Concept ForwardIterator">ForwardIterator</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> |
| </dl></div> |
| </div> |
| <div class="refsect1"> |
| <a name="id1021778"></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::forward_iterator_tag</span>. |
| </p></dd> |
| </dl></div> |
| </div> |
| <div class="refsect1"> |
| <a name="id1021797"></a><h2>Valid expressions</h2> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| <col> |
| <col> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th>Name</th> |
| <th>Expression</th> |
| <th>Type</th> |
| <th>Precondition</th> |
| <th>Semantics</th> |
| <th>Postcondition</th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td><p>Dereference</p></td> |
| <td><p>*i</p></td> |
| <td><p><span class="type">const-if-not-mutable value_type &</span></p></td> |
| <td><p><code class="computeroutput">i</code> is incrementable (not |
| off-the-end)</p></td> |
| <td> </td> |
| <td> </td> |
| </tr> |
| <tr> |
| <td><p>Member access</p></td> |
| <td><p>i->{member-name} (return type is pointer-to-object type)</p></td> |
| <td><p><span class="type">const-if-not-mutable value_type *</span></p></td> |
| <td><p><code class="computeroutput">i</code> is incrementable (not |
| off-the-end)</p></td> |
| <td> </td> |
| <td> </td> |
| </tr> |
| <tr> |
| <td><p>Preincrement</p></td> |
| <td><p>++i</p></td> |
| <td><p><span class="type">Iter &</span></p></td> |
| <td><p><code class="computeroutput">i</code> is incrementable (not |
| off-the-end)</p></td> |
| <td> </td> |
| <td> </td> |
| </tr> |
| <tr> |
| <td><p>Postincrement</p></td> |
| <td><p>i++</p></td> |
| <td><p><span class="type">Iter</span></p></td> |
| <td><p><code class="computeroutput">i</code> is incrementable (not |
| off-the-end)</p></td> |
| <td><p>Equivalent to <code class="computeroutput">{Iter j = i; ++i; return j;}</code></p></td> |
| <td><p><code class="computeroutput">i</code> is dereferenceable or |
| off-the-end</p></td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <div class="refsect1"> |
| <a name="id1021931"></a><h2>Complexity</h2> |
| <p> |
| All iterator operations must take amortized constant time. |
| </p> |
| </div> |
| <div class="refsect1"> |
| <a name="id1021938"></a><h2>Invariants</h2> |
| <div class="variablelist"><dl> |
| <dt><span class="term">Predecrement must return object</span></dt> |
| <dd><p> |
| <code class="computeroutput">&i = &(++i)</code> |
| </p></dd> |
| <dt><span class="term">Unique path through sequence</span></dt> |
| <dd><p> |
| <code class="computeroutput">i == j</code> implies <code class="computeroutput">++i == ++j</code> |
| </p></dd> |
| </dl></div> |
| </div> |
| <div class="refsect1"> |
| <a name="id1021973"></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::hash_set<T>::iterator</span></span></li> |
| </ul></div> |
| </div> |
| <div class="refsect1"> |
| <a name="id1021994"></a><h2>See also</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></ul></div> |
| </div> |
| </div> |
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| <td align="right"><div class="copyright-footer">Copyright © 2001, 2002 Indiana University<br>Copyright © 2000, 2001 University of Notre Dame du Lac<br>Copyright © 2000 Jeremy Siek, Lie-Quan Lee, Andrew Lumsdaine<br>Copyright © 1996-1999 Silicon Graphics Computer Systems, Inc.<br>Copyright © 1994 Hewlett-Packard Company<p>Distributed under the Boost Software License, Version 1.0. |
| (See accompanying file <code class="filename">LICENSE_1_0.txt</code> 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> |
| <p>This product includes software developed at the University |
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| University. For technical information contact Andrew Lumsdaine |
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| Indianapolis, Indiana 46202, phone 317-278-4100, fax |
| 317-274-5902.</p> |
| <p>Some concepts based on versions from the MTL draft manual |
| and Boost Graph and Property Map documentation, the SGI Standard |
| Template Library documentation and the Hewlett-Packard STL, |
| under the following license: |
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