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adding fusion docs and tests [SVN r34920]
2006-08-22 15:57:13 +00:00
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<div class="section" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="fusion.support.is_view"></a><a href="is_view.html" title="is_view">is_view</a></h3></div></div></div>
<a name="fusion.support.is_view.description"></a><h4>
<a name="id447156"></a>
<a href="is_view.html#fusion.support.is_view.description">Description</a>
</h4>
<p>
Metafunction that evaluates to <tt class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span></tt>
if a certain type <tt class="computeroutput"><span class="identifier">T</span></tt> is a
conforming Fusion <a href="../sequences/views.html" title="Views">View</a>, <tt class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">false_</span></tt>
otherwise. A view is a specialized sequence that does not actually contain
data. Views hold sequences which may be other views. In general, views are
held by other views by value, while non-views are held by other views by
reference. <tt class="computeroutput"><span class="identifier">is_view</span></tt> may be
specialized to accomodate clients providing Fusion conforming views.
</p>
<a name="fusion.support.is_view.synopsis"></a><h4>
<a name="id447257"></a>
<a href="is_view.html#fusion.support.is_view.synopsis">Synopsis</a>
</h4>
<pre class="programlisting">
<span class="keyword">namespace</span> <span class="identifier">traits</span>
<span class="special">{</span>
<span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">is_view</span>
<span class="special">{</span>
<span class="keyword">typedef</span> <span class="emphasis"><em>unspecified</em></span> <span class="identifier">type</span><span class="special">;</span>
<span class="special">};</span>
<span class="special">}</span>
</pre>
<a name="fusion.support.is_view.parameters"></a><h4>
<a name="id447386"></a>
<a href="is_view.html#fusion.support.is_view.parameters">Parameters</a>
</h4>
<div class="informaltable">
<h4>
<a name="id447407"></a>
</h4>
<table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>Parameter</th>
<th>Requirement</th>
<th>Description</th>
</tr></thead>
<tbody><tr>
<td><tt class="computeroutput"><span class="identifier">T</span></tt></td>
<td>Any
type</td>
<td>The type to query.</td>
</tr></tbody>
</table>
</div>
<a name="fusion.support.is_view.expression_semantics"></a><h4>
<a name="id447470"></a>
<a href="is_view.html#fusion.support.is_view.expression_semantics">Expression Semantics</a>
</h4>
<pre class="programlisting">
<span class="keyword">typedef</span> <span class="identifier">traits</span><span class="special">::</span><span class="identifier">is_view</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">type</span> <span class="identifier">c</span><span class="special">;</span>
</pre>
<p>
<span class="bold"><b>Return type</b></span>: An MPL Boolean Constant.
</p>
<p>
<span class="bold"><b>Semantics</b></span>: Metafunction that evaluates to
<tt class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span></tt> if a certain type <tt class="computeroutput"><span class="identifier">T</span></tt>
is a conforming Fusion view, <tt class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">false_</span></tt>
otherwise.
</p>
<a name="fusion.support.is_view.header"></a><h4>
<a name="id447622"></a>
<a href="is_view.html#fusion.support.is_view.header">Header</a>
</h4>
<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">support</span><span class="special">/</span><span class="identifier">is_view</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
</pre>
<a name="fusion.support.is_view.example"></a><h4>
<a name="id447710"></a>
<a href="is_view.html#fusion.support.is_view.example">Example</a>
</h4>
<pre class="programlisting">
<span class="identifier">BOOST_MPL_ASSERT_NOT</span><span class="special">((</span> <span class="identifier">traits</span><span class="special">::</span><span class="identifier">is_view</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="special">&gt;</span> <span class="special">));</span>
<span class="identifier">BOOST_MPL_ASSERT_NOT</span><span class="special">((</span> <span class="identifier">traits</span><span class="special">::</span><span class="identifier">is_view</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="special">));</span>
<span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">_</span>
<span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">is_pointer</span><span class="special">;</span>
<span class="keyword">typedef</span> <a href="../sequences/containers/vector.html" title="vector"><tt class="computeroutput"><span class="identifier">vector</span></tt></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">long</span><span class="special">*,</span> <span class="keyword">bool</span><span class="special">,</span> <span class="keyword">double</span><span class="special">&gt;</span> <span class="identifier">vector_type</span><span class="special">;</span>
<span class="keyword">typedef</span> <a href="../sequences/views/filter_view.html" title="filter_view"><tt class="computeroutput"><span class="identifier">filter_view</span></tt></a><span class="special">&lt;</span><span class="identifier">vector_type</span><span class="special">,</span> <span class="identifier">is_pointer</span><span class="special">&lt;</span><span class="identifier">_</span><span class="special">&gt;</span> <span class="special">&gt;</span> <span class="identifier">filter_view_type</span><span class="special">;</span>
<span class="identifier">BOOST_MPL_ASSERT</span><span class="special">((</span> <span class="identifier">traits</span><span class="special">::</span><span class="identifier">is_view</span><span class="special">&lt;</span><span class="identifier">filter_view_type</span><span class="special">&gt;</span> <span class="special">));</span>
</pre>
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