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<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="fusion.iterator.concepts.forward_iterator"></a><a class="link" href="forward_iterator.html" title="Forward Iterator">Forward
Iterator</a>
</h4></div></div></div>
<a name="fusion.iterator.concepts.forward_iterator.description"></a><h6>
<a name="id884575"></a>
<a class="link" href="forward_iterator.html#fusion.iterator.concepts.forward_iterator.description">Description</a>
</h6>
<p>
A Forward Iterator traverses a <a class="link" href="../../sequence.html" title="Sequence">Sequence</a>
allowing movement in only one direction through it's elements, one element
at a time.
</p>
<div class="variablelist">
<p class="title"><b>Notation</b></p>
<dl>
<dt><span class="term"><code class="computeroutput"><span class="identifier">i</span></code>, <code class="computeroutput"><span class="identifier">j</span></code></span></dt>
<dd><p>
Forward Iterators
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">I</span></code>, <code class="computeroutput"><span class="identifier">J</span></code></span></dt>
<dd><p>
Forward Iterator types
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">M</span></code></span></dt>
<dd><p>
An <a href="http://www.boost.org/libs/mpl/index.html" target="_top">MPL</a>
integral constant
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">N</span></code></span></dt>
<dd><p>
An integral constant
</p></dd>
</dl>
</div>
<a name="fusion.iterator.concepts.forward_iterator.expression_requirements"></a><h6>
<a name="id884700"></a>
<a class="link" href="forward_iterator.html#fusion.iterator.concepts.forward_iterator.expression_requirements">Expression
requirements</a>
</h6>
<p>
A type models Forward Iterator if, in addition to being CopyConstructable,
the following expressions are valid:
</p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Expression
</p>
</th>
<th>
<p>
Return type
</p>
</th>
<th>
<p>
Runtime Complexity
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<code class="computeroutput"><a class="link" href="../functions/next.html" title="next"><code class="computeroutput"><span class="identifier">next</span></code></a><span class="special">(</span><span class="identifier">i</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
<a class="link" href="forward_iterator.html" title="Forward Iterator">Forward
Iterator</a>
</p>
</td>
<td>
<p>
Constant
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">i</span> <span class="special">==</span>
<span class="identifier">j</span></code>
</p>
</td>
<td>
<p>
Convertible to bool
</p>
</td>
<td>
<p>
Constant
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">i</span> <span class="special">!=</span>
<span class="identifier">j</span></code>
</p>
</td>
<td>
<p>
Convertible to bool
</p>
</td>
<td>
<p>
Constant
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><a class="link" href="../functions/advance_c.html" title="advance_c"><code class="computeroutput"><span class="identifier">advance_c</span></code></a><span class="special"><</span><span class="identifier">N</span><span class="special">>(</span><span class="identifier">i</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
<a class="link" href="forward_iterator.html" title="Forward Iterator">Forward
Iterator</a>
</p>
</td>
<td>
<p>
Constant
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><a class="link" href="../functions/advance.html" title="advance"><code class="computeroutput"><span class="identifier">advance</span></code></a><span class="special"><</span><span class="identifier">M</span><span class="special">>(</span><span class="identifier">i</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
<a class="link" href="forward_iterator.html" title="Forward Iterator">Forward
Iterator</a>
</p>
</td>
<td>
<p>
Constant
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><a class="link" href="../functions/distance.html" title="distance"><code class="computeroutput"><span class="identifier">distance</span></code></a><span class="special">(</span><span class="identifier">i</span><span class="special">,</span>
<span class="identifier">j</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><a class="link" href="../metafunctions/distance.html" title="distance"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">distance</span></code></a><span class="special"><</span><span class="identifier">I</span><span class="special">,</span>
<span class="identifier">J</span><span class="special">>::</span><span class="identifier">type</span></code>
</p>
</td>
<td>
<p>
Constant
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><a class="link" href="../functions/deref.html" title="deref"><code class="computeroutput"><span class="identifier">deref</span></code></a><span class="special">(</span><span class="identifier">i</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><a class="link" href="../metafunctions/deref.html" title="deref"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">deref</span></code></a><span class="special"><</span><span class="identifier">I</span><span class="special">>::</span><span class="identifier">type</span></code>
</p>
</td>
<td>
<p>
Constant
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="special">*</span><span class="identifier">i</span></code>
</p>
</td>
<td>
<p>
<code class="computeroutput"><a class="link" href="../metafunctions/deref.html" title="deref"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">deref</span></code></a><span class="special"><</span><span class="identifier">I</span><span class="special">>::</span><span class="identifier">type</span></code>
</p>
</td>
<td>
<p>
Constant
</p>
</td>
</tr>
</tbody>
</table></div>
<a name="fusion.iterator.concepts.forward_iterator.meta_expressions"></a><h6>
<a name="id885271"></a>
<a class="link" href="forward_iterator.html#fusion.iterator.concepts.forward_iterator.meta_expressions">Meta
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="../metafunctions/next.html" title="next"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">next</span></code></a><span class="special"><</span><span class="identifier">I</span><span class="special">>::</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="../metafunctions/equal_to.html" title="equal_to"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">equal_to</span></code></a><span class="special"><</span><span class="identifier">I</span><span class="special">,</span>
<span class="identifier">J</span><span class="special">>::</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="../metafunctions/advance_c.html" title="advance_c"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">advance_c</span></code></a><span class="special"><</span><span class="identifier">I</span><span class="special">,</span>
<span class="identifier">N</span><span class="special">>::</span><span class="identifier">type</span></code>
</p>
</td>
<td>
<p>
Linear
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><a class="link" href="../metafunctions/advance.html" title="advance"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">advance</span></code></a><span class="special"><</span><span class="identifier">I</span> <span class="special">,</span><span class="identifier">M</span><span class="special">>::</span><span class="identifier">type</span></code>
</p>
</td>
<td>
<p>
Linear
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><a class="link" href="../metafunctions/distance.html" title="distance"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">distance</span></code></a><span class="special"><</span><span class="identifier">I</span> <span class="special">,</span><span class="identifier">J</span><span class="special">>::</span><span class="identifier">type</span></code>
</p>
</td>
<td>
<p>
Linear
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><a class="link" href="../metafunctions/deref.html" title="deref"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">deref</span></code></a><span class="special"><</span><span class="identifier">I</span><span class="special">>::</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="../metafunctions/value_of.html" title="value_of"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">value_of</span></code></a><span class="special"><</span><span class="identifier">I</span><span class="special">>::</span><span class="identifier">type</span></code>
</p>
</td>
<td>
<p>
Amortized constant time
</p>
</td>
</tr>
</tbody>
</table></div>
<a name="fusion.iterator.concepts.forward_iterator.expression_semantics"></a><h6>
<a name="id885725"></a>
<a class="link" href="forward_iterator.html#fusion.iterator.concepts.forward_iterator.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="../functions/next.html" title="next"><code class="computeroutput"><span class="identifier">next</span></code></a><span class="special">(</span><span class="identifier">i</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
An iterator to the element following <code class="computeroutput"><span class="identifier">i</span></code>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">i</span> <span class="special">==</span>
<span class="identifier">j</span></code>
</p>
</td>
<td>
<p>
Iterator equality comparison
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">i</span> <span class="special">!=</span>
<span class="identifier">j</span></code>
</p>
</td>
<td>
<p>
Iterator inequality comparison
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><a class="link" href="../functions/advance_c.html" title="advance_c"><code class="computeroutput"><span class="identifier">advance_c</span></code></a><span class="special"><</span><span class="identifier">N</span><span class="special">>(</span><span class="identifier">i</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
An iterator n elements after <code class="computeroutput"><span class="identifier">i</span></code>
in the sequence
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><a class="link" href="../functions/advance.html" title="advance"><code class="computeroutput"><span class="identifier">advance</span></code></a><span class="special"><</span><span class="identifier">M</span><span class="special">>(</span><span class="identifier">i</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
Equivalent to <code class="computeroutput"><span class="identifier">advance_c</span><span class="special"><</span><span class="identifier">M</span><span class="special">::</span><span class="identifier">value</span><span class="special">>(</span><span class="identifier">i</span><span class="special">)</span></code>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><a class="link" href="../functions/distance.html" title="distance"><code class="computeroutput"><span class="identifier">distance</span></code></a><span class="special">(</span><span class="identifier">i</span><span class="special">,</span>
<span class="identifier">j</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
The number of elements between <code class="computeroutput"><span class="identifier">i</span></code>
and <code class="computeroutput"><span class="identifier">j</span></code>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><a class="link" href="../functions/deref.html" title="deref"><code class="computeroutput"><span class="identifier">deref</span></code></a><span class="special">(</span><span class="identifier">i</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
The element at position<code class="computeroutput"><span class="identifier">i</span></code>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="special">*</span><span class="identifier">i</span></code>
</p>
</td>
<td>
<p>
Equivalent to <code class="computeroutput"><span class="identifier">deref</span><span class="special">(</span><span class="identifier">i</span><span class="special">)</span></code>
</p>
</td>
</tr>
</tbody>
</table></div>
<a name="fusion.iterator.concepts.forward_iterator.invariants"></a><h6>
<a name="id886188"></a>
<a class="link" href="forward_iterator.html#fusion.iterator.concepts.forward_iterator.invariants">Invariants</a>
</h6>
<p>
The following invariants always hold:
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
<code class="computeroutput"><span class="special">!(</span><span class="identifier">i</span>
<span class="special">==</span> <span class="identifier">j</span><span class="special">)</span> <span class="special">==</span> <span class="special">(</span><span class="identifier">i</span> <span class="special">!=</span> <span class="identifier">j</span><span class="special">)</span></code>
</li>
<li class="listitem">
<code class="computeroutput"><a class="link" href="../functions/next.html" title="next"><code class="computeroutput"><span class="identifier">next</span></code></a><span class="special">(</span><span class="identifier">i</span><span class="special">)</span> <span class="special">==</span> <a class="link" href="../functions/advance_c.html" title="advance_c"><code class="computeroutput"><span class="identifier">advance_c</span></code></a><span class="special"><</span><span class="number">1</span><span class="special">>(</span><span class="identifier">i</span><span class="special">)</span></code>
</li>
<li class="listitem">
<code class="computeroutput"><a class="link" href="../functions/distance.html" title="distance"><code class="computeroutput"><span class="identifier">distance</span></code></a><span class="special">(</span><span class="identifier">i</span><span class="special">,</span> <a class="link" href="../functions/advance_c.html" title="advance_c"><code class="computeroutput"><span class="identifier">advance_c</span></code></a><span class="special"><</span><span class="identifier">N</span><span class="special">>(</span><span class="identifier">i</span><span class="special">))</span> <span class="special">==</span> <span class="identifier">N</span></code>
</li>
<li class="listitem">
Using <code class="computeroutput"><a class="link" href="../functions/next.html" title="next"><code class="computeroutput"><span class="identifier">next</span></code></a></code> to traverse the
sequence will never return to a previously seen position
</li>
<li class="listitem">
<code class="computeroutput"><a class="link" href="../functions/deref.html" title="deref"><code class="computeroutput"><span class="identifier">deref</span></code></a><span class="special">(</span><span class="identifier">i</span><span class="special">)</span></code>
is equivalent to <code class="computeroutput"><span class="special">*</span><span class="identifier">i</span></code>
</li>
<li class="listitem">
If <code class="computeroutput"><span class="identifier">i</span> <span class="special">==</span>
<span class="identifier">j</span></code> then <code class="computeroutput"><span class="special">*</span><span class="identifier">i</span></code> is equivalent to <code class="computeroutput"><span class="special">*</span><span class="identifier">j</span></code>
</li>
</ul></div>
<a name="fusion.iterator.concepts.forward_iterator.models"></a><h6>
<a name="id887049"></a>
<a class="link" href="forward_iterator.html#fusion.iterator.concepts.forward_iterator.models">Models</a>
</h6>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
<a class="link" href="../../adapted/std__pair.html" title="std::pair"><code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span></code></a>
iterator
</li>
<li class="listitem">
<a class="link" href="../../adapted/boost__array.html" title="boost::array"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">array</span></code></a>
iterator
</li>
<li class="listitem">
<a class="link" href="../../container/vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a>
iterator
</li>
<li class="listitem">
<a class="link" href="../../container/cons.html" title="cons"><code class="computeroutput"><span class="identifier">cons</span></code></a>
iterator
</li>
<li class="listitem">
<a class="link" href="../../container/list.html" title="list"><code class="computeroutput"><span class="identifier">list</span></code></a>
iterator
</li>
<li class="listitem">
<a class="link" href="../../container/set.html" title="set"><code class="computeroutput"><span class="identifier">set</span></code></a>
iterator
</li>
<li class="listitem">
<a class="link" href="../../container/map.html" title="map"><code class="computeroutput"><span class="identifier">map</span></code></a>
iterator
</li>
<li class="listitem">
<a class="link" href="../../view/single_view.html" title="single_view"><code class="computeroutput"><span class="identifier">single_view</span></code></a>
iterator
</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>
iterator
</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>
iterator
</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>
iterator
</li>
<li class="listitem">
<a class="link" href="../../view/transform_view.html" title="transform_view"><code class="computeroutput"><span class="identifier">transform_view</span></code></a>
iterator
</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>
iterator
</li>
</ul></div>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright © 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>
</div></td>
</tr></table>
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