<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>Function unpack_expr</title>
<link rel="stylesheet" href="../../boostbook.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.75.2">
<link rel="home" href="../../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset">
<link rel="up" href="../../proto/reference.html#header.boost.proto.make_expr_hpp" title="Header <boost/proto/make_expr.hpp>">
<link rel="prev" href="make_expr_id1241909.html" title="Function make_expr">
<link rel="next" href="_.html" title="Struct _">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table cellpadding="2" width="100%"><tr>
<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td>
<td align="center"><a href="../../../../index.html">Home</a></td>
<td align="center"><a href="../../../../libs/libraries.htm">Libraries</a></td>
<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
<td align="center"><a href="../../../../more/index.htm">More</a></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="make_expr_id1241909.html"><img src="../../../../doc/html/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../proto/reference.html#header.boost.proto.make_expr_hpp"><img src="../../../../doc/html/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../doc/html/images/home.png" alt="Home"></a><a accesskey="n" href="_.html"><img src="../../../../doc/html/images/next.png" alt="Next"></a>
</div>
<div class="refentry" title="Function unpack_expr">
<a name="boost.proto.unpack_expr_id1242154"></a><div class="titlepage"></div>
<div class="refnamediv">
<h2><span class="refentrytitle">Function unpack_expr</span></h2>
<p>boost::proto::unpack_expr — Construct an expression of the requested tag type with a domain and with children
from the specified Fusion Forward Sequence.</p>
</div>
<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.make_expr_hpp" title="Header <boost/proto/make_expr.hpp>">boost/proto/make_expr.hpp</a>>
</em></span>
<span class="bold"><strong>template</strong></span><<span class="bold"><strong>typename</strong></span> Tag, <span class="bold"><strong>typename</strong></span> Sequence>
<span class="type"><span class="bold"><strong>typename</strong></span> <a class="link" href="result_of/unpack_expr.html" title="Struct template unpack_expr">proto::result_of::unpack_expr</a><Tag, Sequence <span class="bold"><strong>const</strong></span>>::type <span class="bold"><strong>const</strong></span></span>
unpack_expr(Sequence <span class="bold"><strong>const</strong></span> & sequence);
<span class="bold"><strong>template</strong></span><<span class="bold"><strong>typename</strong></span> Tag, <span class="bold"><strong>typename</strong></span> Domain, <span class="bold"><strong>typename</strong></span> Sequence>
<span class="type"><span class="bold"><strong>typename</strong></span> <a class="link" href="result_of/unpack_expr.html" title="Struct template unpack_expr">proto::result_of::unpack_expr</a><Tag, Domain, Sequence <span class="bold"><strong>const</strong></span>>::type <span class="bold"><strong>const</strong></span></span>
unpack_expr(Sequence <span class="bold"><strong>const</strong></span> & sequence);</pre></div>
<div class="refsect1" title="Description">
<a name="id1596632"></a><h2>Description</h2>
<p>
This function template may be invoked either with or without specifying a
<code class="computeroutput">Domain</code> argument. If no domain is specified, the domain is
deduced by examining in order the domains of the elements of <code class="computeroutput">sequence</code>
and taking the first that is not
<code class="computeroutput"><code class="computeroutput"><a class="link" href="default_domain.html" title="Struct default_domain">proto::default_domain</a></code></code>, if any such domain
exists, or <code class="computeroutput"><code class="computeroutput"><a class="link" href="default_domain.html" title="Struct default_domain">proto::default_domain</a></code></code> otherwise.
</p>
<p>
Let <code class="computeroutput">s</code> be a Fusion Random Access Sequence equivalent to
<code class="computeroutput">sequence</code>.
Let <code class="computeroutput"><em class="replaceable"><code>WRAP</code></em><N>(s)</code>, where
<code class="computeroutput">s</code> has type <code class="computeroutput">S</code>, be defined such that:
</p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem"><p>
If <code class="computeroutput">fusion::result_of::value_at_c<S,N>::type</code> is a reference,
<code class="computeroutput"><em class="replaceable"><code>WRAP</code></em><N>(s)</code> is equivalent to
<code class="computeroutput"><code class="computeroutput"><a class="link" href="as_child_id1264710.html" title="Function as_child">proto::as_child</a></code><Domain>(fusion::at_c<N>(s))</code>.
</p></li>
<li class="listitem"><p>
Otherwise, <code class="computeroutput"><em class="replaceable"><code>WRAP</code></em><N>(s)</code> is equivalent to
<code class="computeroutput"><code class="computeroutput"><a class="link" href="as_expr_id1264483.html" title="Function as_expr">proto::as_expr</a></code><Domain>(fusion::at_c<N>(s))</code>.
</p></li>
</ul></div>
<p>
Let <code class="computeroutput"><em class="replaceable"><code>MAKE</code></em><Tag>(a...)</code> be defined as
<code class="computeroutput"><code class="computeroutput"><a class="link" href="expr.html" title="Struct template expr">proto::expr</a></code><Tag,
<code class="computeroutput"><a class="link" href="listN.html" title="Struct template listN">proto::listN</a></code><A...> >::make(a...)</code>
where
<code class="computeroutput">A<sub>x</sub></code> is the type of
<code class="computeroutput">a<sub>x</sub></code>.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term">Parameters:</span></p></td>
<td><div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody><tr>
<td><p><span class="term"><code class="computeroutput">sequence</code></span></p></td>
<td><p>A Fusion Forward Sequence.</p></td>
</tr></tbody>
</table></div></td>
</tr>
<tr>
<td><p><span class="term">Returns:</span></p></td>
<td><p>
<code class="computeroutput">Domain()(<em class="replaceable"><code>MAKE</code></em><Tag>(<em class="replaceable"><code>WRAP</code></em><0>(s),...
<em class="replaceable"><code>WRAP</code></em><<em class="replaceable"><code>N</code></em>-1>(s)))</code>, where
<em class="replaceable"><code>N</code></em> is the size of <code class="computeroutput">Sequence</code>.
</p></td>
</tr>
</tbody>
</table></div>
</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 © 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>)
</p>
</div></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="make_expr_id1241909.html"><img src="../../../../doc/html/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../proto/reference.html#header.boost.proto.make_expr_hpp"><img src="../../../../doc/html/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../doc/html/images/home.png" alt="Home"></a><a accesskey="n" href="_.html"><img src="../../../../doc/html/images/next.png" alt="Next"></a>
</div>
</body>
</html>
