1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<head> 4<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 5<title>Struct template unpack_expr</title> 6<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css"> 7<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 8<link rel="home" href="../../../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> 9<link rel="up" href="../../../proto/reference.html#header.boost.proto.make_expr_hpp" title="Header <boost/proto/make_expr.hpp>"> 10<link rel="prev" href="make_e_1_3_33_5_31_2_1_2_2.html" title="Struct template make_expr<Tag, Domain, A...>"> 11<link rel="next" href="unpack_1_3_33_5_31_2_1_2_4.html" title="Struct template unpack_expr<Tag, Domain, Sequence>"> 12</head> 13<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 14<table cellpadding="2" width="100%"><tr> 15<td 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src="../../../../../doc/src/images/next.png" alt="Next"></a> 25</div> 26<div class="refentry"> 27<a name="boost.proto.result_of.unpack_expr"></a><div class="titlepage"></div> 28<div class="refnamediv"> 29<h2><span class="refentrytitle">Struct template unpack_expr</span></h2> 30<p>boost::proto::result_of::unpack_expr — Metafunction that computes the return type of the 31 <code class="computeroutput"><a class="link" href="../unpack_expr.html" title="Function unpack_expr">proto::unpack_expr()</a></code> 32 function, with a domain deduced from the domains of the children. 33 </p> 34</div> 35<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> 36<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// 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>> 37 38</span><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Tag<span class="special">,</span> <span class="keyword">typename</span> Sequence<span class="special">,</span> <span class="keyword">typename</span> Void <span class="special">=</span> <span class="keyword">void</span><span class="special">></span> 39<span class="keyword">struct</span> <a class="link" href="unpack_expr.html" title="Struct template unpack_expr">unpack_expr</a> <span class="special">{</span> 40 <span class="comment">// types</span> 41 <span class="keyword">typedef</span> 42 <span class="keyword">typename</span> <a class="link" href="make_expr.html" title="Struct template make_expr">proto::result_of::make_expr</a><span class="special"><</span> 43 <span class="identifier">Tag</span><span class="special">,</span> 44 <span class="keyword">typename</span> <span class="identifier">fusion</span><span class="special">::</span><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">value_at_c</span><span class="special"><</span><em class="replaceable"><code><span class="identifier">S</span></code></em><span class="special">,</span> <span class="number">0</span><span class="special">></span><span class="special">::</span><span class="identifier">type</span><span class="special">,</span> 45 <span class="special">...</span> 46 <span class="keyword">typename</span> <span class="identifier">fusion</span><span class="special">::</span><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">value_at_c</span><span class="special"><</span><em class="replaceable"><code><span class="identifier">S</span></code></em><span class="special">,</span> <em class="replaceable"><code><span class="identifier">N</span></code></em><span class="special">-</span><span class="number">1</span><span class="special">></span><span class="special">::</span><span class="identifier">type</span> 47 <span class="special">></span><span class="special">::</span><span class="identifier">type</span> 48 <a name="boost.proto.result_of.unpack_expr.type"></a><span class="identifier">type</span><span class="special">;</span> <span class="comment">// Where S is a Fusion RandomAccessSequence equivalent to Sequence, and N is the size of S.</span> 49<span class="special">}</span><span class="special">;</span></pre></div> 50<div class="refsect1"> 51<a name="id-1.3.33.5.33.8.4"></a><h2>Description</h2> 52<p> 53 Compute the return type of the 54 <code class="computeroutput"><a class="link" href="../unpack_expr.html" title="Function unpack_expr">proto::unpack_expr()</a></code> 55 function. 56 </p> 57<p> 58 <code class="computeroutput">Sequence</code> is a Fusion Forward Sequence. 59 </p> 60<p> 61 In this specialization, the domain is deduced from the domains of the child types. 62 If <code class="computeroutput"><a class="link" href="../is_domain.html" title="Struct template is_domain">proto::is_domain</a><Sequence>::value</code> 63 is <code class="computeroutput">true</code>, then another specialization is selected. 64 </p> 65</div> 66</div> 67<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 68<td align="left"></td> 69<td align="right"><div class="copyright-footer">Copyright © 2008 Eric Niebler<p> 70 Distributed under the Boost Software License, Version 1.0. (See accompanying 71 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>) 72 </p> 73</div></td> 74</tr></table> 75<hr> 76<div class="spirit-nav"> 77<a accesskey="p" href="make_e_1_3_33_5_31_2_1_2_2.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../proto/reference.html#header.boost.proto.make_expr_hpp"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="unpack_1_3_33_5_31_2_1_2_4.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 78</div> 79</body> 80</html> 81
