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<div class="refentry" title="Struct template is_expr">
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<h2><span class="refentrytitle">Struct template is_expr</span></h2>
<p>boost::proto::is_expr — A Boolean metafunction that indicates whether a given type <code class="computeroutput">T</code>
is a Proto expression type.</p>
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<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="emphasis"><em>// In header: <<a class="link" href="../../proto/reference.html#header.boost.proto.traits_hpp" title="Header <boost/proto/traits.hpp>">boost/proto/traits.hpp</a>>
</em></span><span class="bold"><strong>template</strong></span><<span class="bold"><strong>typename</strong></span> T>
<span class="bold"><strong>struct</strong></span> <a class="link" href="is_expr.html" title="Struct template is_expr">is_expr</a> : <span class="bold"><strong></strong></span> <span class="type">mpl::bool_<<em class="replaceable"><code><span class="bold"><strong>true</strong></span>-or-<span class="bold"><strong>false</strong></span></code></em>></span> {
};</pre></div>
<div class="refsect1" title="Description">
<a name="id1659914"></a><h2>Description</h2>
<p>
If <code class="computeroutput">T</code> is an instantiation of <code class="computeroutput">
<a class="link" href="expr.html" title="Struct template expr">proto::expr<></a></code> or is an extension
(via <a class="link" href="extends.html" title="Struct template extends">proto::extends<></a> or
<a class="link" href="../../BOOST_PROTO_EXTENDS.html" title="Macro BOOST_PROTO_EXTENDS">BOOST_PROTO_EXTENDS</a>()) of such an instantiation,
<code class="computeroutput"><a class="link" href="is_expr.html" title="Struct template is_expr">proto::is_expr</a><T>::value</code>
is <code class="computeroutput">true</code>.
Otherwise, <code class="computeroutput"><a class="link" href="is_expr.html" title="Struct template is_expr">proto::is_expr</a><T>::value</code>
is <code class="computeroutput">false</code>.
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<td align="right"><div class="copyright-footer">Copyright © 2008 Eric Niebler<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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