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boost_fusion/doc/html/fusion/view/nview.html
Christopher Schmidt 35e469e2d5 fix for #2355: discrepancy between std::accumulate and fusion::accumulate 
[SVN r57125]
2009-10-24 10:59:01 +00:00

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<html>
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<title>nview</title>
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</div>
<div class="section" title="nview">
<div class="titlepage"><div><div><h3 class="title">
<a name="fusion.view.nview"></a><a class="link" href="nview.html" title="nview">nview</a>
</h3></div></div></div>
<a name="fusion.view.nview.description"></a><h5>
<a name="id779592"></a>
<a class="link" href="nview.html#fusion.view.nview.description">Description</a>
</h5>
<p>
<code class="computeroutput"><span class="identifier">nview</span></code> presents a view which
iterates over a given <a class="link" href="../sequence.html" title="Sequence">Sequence</a> in
a specified order. An <code class="computeroutput"><span class="identifier">nview</span></code>
is constructed from an arbitrary <a class="link" href="../sequence.html" title="Sequence">Sequence</a>
and a list of indicies specifying the elements to iterate over.
</p>
<a name="fusion.view.nview.header"></a><h5>
<a name="id779633"></a>
<a class="link" href="nview.html#fusion.view.nview.header">Header</a>
</h5>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">view</span><span class="special">/</span><span class="identifier">nview</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">nview</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
</pre>
<a name="fusion.view.nview.synopsis"></a><h5>
<a name="id779741"></a>
<a class="link" href="nview.html#fusion.view.nview.synopsis">Synopsis</a>
</h5>
<pre class="programlisting"><span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Sequence</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Indicies</span><span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">nview</span><span class="special">;</span>
<span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Sequence</span><span class="special">,</span> <span class="keyword">int</span> <span class="identifier">I1</span><span class="special">,</span> <span class="keyword">int</span> <span class="identifier">I2</span> <span class="special">=</span> <span class="special">-</span><span class="number">1</span><span class="special">,</span> <span class="special">...&gt;</span>
<span class="keyword">typename</span> <span class="identifier">result_of</span><span class="special">::</span><span class="identifier">nview</span><span class="special">&lt;</span><span class="identifier">Sequence</span><span class="special">,</span> <span class="identifier">I1</span><span class="special">,</span> <span class="identifier">I2</span><span class="special">,</span> <span class="special">...&gt;::</span><span class="identifier">type</span>
<span class="identifier">as_nview</span><span class="special">(</span><span class="identifier">Sequence</span><span class="special">&amp;</span> <span class="identifier">s</span><span class="special">);</span>
</pre>
<a name="fusion.view.nview.template_parameters"></a><h5>
<a name="id782134"></a>
<a class="link" href="nview.html#fusion.view.nview.template_parameters">Template parameters</a>
</h5>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Parameter
</p>
</th>
<th>
<p>
Description
</p>
</th>
<th>
<p>
Default
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">Sequence</span></code>
</p>
</td>
<td>
<p>
An arbitrary Fusion <a class="link" href="../sequence/concepts/forward_sequence.html" title="Forward Sequence">Forward
Sequence</a>
</p>
</td>
<td>
<p>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">Indicies</span></code>
</p>
</td>
<td>
<p>
A <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">vector_c</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span> <span class="special">...&gt;</span></code> holding the indicies defining
the required iteration order.
</p>
</td>
<td>
<p>
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">I1</span></code>, <code class="computeroutput"><span class="identifier">I2</span></code>, <code class="computeroutput"><span class="identifier">I3</span></code>...
</p>
</td>
<td>
<p>
A list of integers specifying the required iteration order.
</p>
</td>
<td>
<p>
<code class="computeroutput"><span class="identifier">INT_MAX</span></code> for <code class="computeroutput"><span class="identifier">I2</span></code>, <code class="computeroutput"><span class="identifier">I3</span></code>...
</p>
</td>
</tr>
</tbody>
</table></div>
<a name="fusion.view.nview.model_of"></a><h5>
<a name="id782347"></a>
<a class="link" href="nview.html#fusion.view.nview.model_of">Model of</a>
</h5>
<div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
<a class="link" href="../sequence/concepts/random_access_sequence.html" title="Random Access Sequence">Random
Access Sequence</a> (see <a class="link" href="../sequence/concepts.html#fusion.sequence.concepts.traversal">Sequence
Traversal Concept</a>)
</li></ul></div>
<div class="variablelist" title="Notation">
<p class="title"><b>Notation</b></p>
<dl>
<dt><span class="term"><code class="computeroutput"><span class="identifier">NV</span></code></span></dt>
<dd><p>
A <code class="computeroutput"><span class="identifier">nview</span></code> type
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">s</span></code></span></dt>
<dd><p>
An instance of <code class="computeroutput"><span class="identifier">Sequences</span></code>
</p></dd>
<dt><span class="term"><code class="computeroutput"><span class="identifier">nv1</span></code>,
<code class="computeroutput"><span class="identifier">nv2</span></code></span></dt>
<dd><p>
Instances of <code class="computeroutput"><span class="identifier">NV</span></code>
</p></dd>
</dl>
</div>
<a name="fusion.view.nview.expression_semantics"></a><h5>
<a name="id782467"></a>
<a class="link" href="nview.html#fusion.view.nview.expression_semantics">Expression Semantics</a>
</h5>
<p>
Semantics of an expression is defined only where it differs from, or is not
defined in <a class="link" href="../sequence/concepts/random_access_sequence.html" title="Random Access Sequence">Random
Access Sequence</a>.
</p>
<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"><span class="identifier">NV</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
Creates an <code class="computeroutput"><span class="identifier">nview</span></code>
given a sequence and a list of indicies.
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">NV</span><span class="special">(</span><span class="identifier">nv1</span><span class="special">)</span></code>
</p>
</td>
<td>
<p>
Copy constructs an <code class="computeroutput"><span class="identifier">nview</span></code>
from another <code class="computeroutput"><span class="identifier">nview</span></code>,
<code class="computeroutput"><span class="identifier">nv1</span></code>.
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">nv1</span> <span class="special">=</span>
<span class="identifier">nv2</span></code>
</p>
</td>
<td>
<p>
Assigns to an <code class="computeroutput"><span class="identifier">nview</span></code>,
<code class="computeroutput"><span class="identifier">nv1</span></code>, from another
<code class="computeroutput"><span class="identifier">nview</span></code>, <code class="computeroutput"><span class="identifier">nv2</span></code>.
</p>
</td>
</tr>
</tbody>
</table></div>
<p>
The <code class="computeroutput"><span class="identifier">nview</span></code> internally stores
a Fusion <a class="link" href="../container/vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a>
of references to the elements of the original Fusion <a class="link" href="../sequence.html" title="Sequence">Sequence</a>
</p>
<a name="fusion.view.nview.example"></a><h5>
<a name="id782710"></a>
<a class="link" href="nview.html#fusion.view.nview.example">Example</a>
</h5>
<pre class="programlisting"><span class="keyword">typedef</span> <a class="link" href="../container/vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span> <span class="keyword">char</span><span class="special">,</span> <span class="keyword">double</span><span class="special">&gt;</span> <span class="identifier">vec</span><span class="special">;</span>
<span class="keyword">typedef</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">vector_c</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span> <span class="number">2</span><span class="special">,</span> <span class="number">1</span><span class="special">,</span> <span class="number">0</span><span class="special">,</span> <span class="number">2</span><span class="special">,</span> <span class="number">0</span><span class="special">&gt;</span> <span class="identifier">indicies</span><span class="special">;</span>
<span class="identifier">vec</span> <span class="identifier">v1</span><span class="special">(</span><span class="number">1</span><span class="special">,</span> <span class="char">'c'</span><span class="special">,</span> <span class="number">2.0</span><span class="special">);</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">nview</span><span class="special">&lt;</span><span class="identifier">vec</span><span class="special">,</span> <span class="identifier">indicies</span><span class="special">&gt;(</span><span class="identifier">v1</span><span class="special">)</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> <span class="comment">// (2.0 c 1 2.0 1)
</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">as_nview</span><span class="special">&lt;</span><span class="number">2</span><span class="special">,</span> <span class="number">1</span><span class="special">,</span> <span class="number">1</span><span class="special">,</span> <span class="number">0</span><span class="special">&gt;(</span><span class="identifier">v1</span><span class="special">)</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> <span class="comment">// (2.0 c c 1)
</span></pre>
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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>)
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