1<?xml version="1.0" encoding="utf-8" ?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> 4<head> 5<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 6<meta name="generator" content="Docutils 0.7: http://docutils.sourceforge.net/" /> 7<title>The MPL Reference Manual: apply_wrap</title> 8<link rel="stylesheet" href="../style.css" type="text/css" /> 9</head> 10<body class="docframe refmanual"> 11<table class="header"><tr class="header"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./apply.html" class="navigation-link">Prev</a> <a href="./unpack-args.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./apply.html" class="navigation-link">Back</a> <a href="./unpack-args.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./invocation.html" class="navigation-link">Up</a> <a href="../refmanual.html" class="navigation-link">Home</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./refmanual_toc.html" class="navigation-link">Full TOC</a></span></td> 12<td class="header-group page-location"><a href="../refmanual.html" class="navigation-link">Front Page</a> / <a href="./metafunctions.html" class="navigation-link">Metafunctions</a> / <a href="./invocation.html" class="navigation-link">Invocation</a> / <a href="./apply-wrap.html" class="navigation-link">apply_wrap</a></td> 13</tr></table><div class="header-separator"></div> 14<div class="section" id="apply-wrap"> 15<h1><a class="toc-backref" href="./invocation.html#id1526">apply_wrap</a></h1> 16<div class="section" id="id894"> 17<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> 18<pre class="literal-block"> 19template< 20 typename F 21 > 22struct apply_wrap0 23{ 24 typedef <em>unspecified</em> type; 25}; 26 27template< 28 typename F, typename A1 29 > 30struct apply_wrap1 31{ 32 typedef <em>unspecified</em> type; 33}; 34 35<em>...</em> 36 37template< 38 typename F, typename A1,<em>...</em> typename An 39 > 40struct <a href="./apply-wrap.html" class="identifier">apply_wrap</a><em>n</em> 41{ 42 typedef <em>unspecified</em> type; 43}; 44</pre> 45</div> 46<div class="section" id="id895"> 47<h3><a class="subsection-title" href="#description" name="description">Description</a></h3> 48<p>Invokes a <a class="reference internal" href="./metafunction-class.html">Metafunction Class</a> <tt class="literal"><span class="pre">F</span></tt> with arguments <tt class="literal"><span class="pre">A1</span></tt>,... <tt class="literal"><span class="pre">An</span></tt>.</p> 49<p>In essence, <tt class="literal"><span class="pre"><a href="./apply-wrap.html" class="identifier">apply_wrap</a></span></tt> forms are nothing more than syntactic wrappers around 50<tt class="literal"><span class="pre">F::<a href="./apply.html" class="identifier">apply</a><A1,...</span> <span class="pre">An>::type</span></tt> / <tt class="literal"><span class="pre">F::<a href="./apply.html" class="identifier">apply</a>::type</span></tt> expressions (hence the name). 51They provide a more concise notation and higher portability than their 52underlaying constructs at the cost of an extra template instantiation.</p> 53</div> 54<div class="section" id="id896"> 55<h3><a class="subsection-title" href="#header" name="header">Header</a></h3> 56<pre class="literal-block"> 57#include <<a href="../../../../boost/mpl/apply_wrap.hpp" class="header">boost/mpl/apply_wrap.hpp</a>> 58</pre> 59</div> 60<div class="section" id="id897"> 61<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> 62<table border="1" class="docutils table"> 63<colgroup> 64<col width="15%" /> 65<col width="36%" /> 66<col width="48%" /> 67</colgroup> 68<thead valign="bottom"> 69<tr><th class="head">Parameter</th> 70<th class="head">Requirement</th> 71<th class="head">Description</th> 72</tr> 73</thead> 74<tbody valign="top"> 75<tr><td><tt class="literal"><span class="pre">F</span></tt></td> 76<td><a class="reference internal" href="./metafunction-class.html">Metafunction Class</a></td> 77<td>A metafunction class to invoke.</td> 78</tr> 79<tr><td><tt class="literal"><span class="pre">A1</span></tt>,... <tt class="literal"><span class="pre">An</span></tt></td> 80<td>Any type</td> 81<td>Invocation arguments.</td> 82</tr> 83</tbody> 84</table> 85</div> 86<div class="section" id="id898"> 87<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> 88<p>For any <a class="reference internal" href="./metafunction-class.html">Metafunction Class</a> <tt class="literal"><span class="pre">f</span></tt> and arbitrary types <tt class="literal"><span class="pre">a1</span></tt>,... <tt class="literal"><span class="pre">an</span></tt>:</p> 89<pre class="literal-block"> 90typedef <a href="./apply-wrap.html" class="identifier">apply_wrap</a><em>n</em><f,a1,<em>...</em>an>::type t; 91</pre> 92<table class="docutils field-list" frame="void" rules="none"> 93<col class="field-name" /> 94<col class="field-body" /> 95<tbody valign="top"> 96<tr class="field"><th class="field-name">Return type:</th><td class="field-body">Any type.</td> 97</tr> 98<tr class="field"><th class="field-name">Semantics:</th><td class="field-body">If <tt class="literal"><span class="pre">n</span> <span class="pre">></span> <span class="pre">0</span></tt>, equivalent to <tt class="literal"><span class="pre">typedef</span> <span class="pre">f::<a href="./apply.html" class="identifier">apply</a><a1,...</span> <span class="pre">an>::type</span> <span class="pre">t;</span></tt>, 99otherwise equivalent to either <tt class="literal"><span class="pre">typedef</span> <span class="pre">f::<a href="./apply.html" class="identifier">apply</a>::type</span> <span class="pre">t;</span></tt> or 100<tt class="literal"><span class="pre">typedef</span> <span class="pre">f::<a href="./apply.html" class="identifier">apply</a><>::type</span> <span class="pre">t;</span></tt> depending on whether <tt class="literal"><span class="pre">f::<a href="./apply.html" class="identifier">apply</a></span></tt> is 101a class or a class template.</td> 102</tr> 103</tbody> 104</table> 105</div> 106<div class="section" id="id899"> 107<h3><a class="subsection-title" href="#example" name="example">Example</a></h3> 108<pre class="literal-block"> 109struct f0 110{ 111 template< typename T = int > struct <a href="./apply.html" class="identifier">apply</a> 112 { 113 typedef char type; 114 }; 115}; 116 117struct g0 118{ 119 struct <a href="./apply.html" class="identifier">apply</a> { typedef char type; }; 120}; 121 122struct f2 123{ 124 template< typename T1, typename T2 > struct <a href="./apply.html" class="identifier">apply</a> 125 { 126 typedef T2 type; 127 }; 128}; 129 130 131typedef <a href="./apply-wrap.html" class="identifier">apply_wrap</a><tt class="literal"><span class="pre">0</span></tt>< f0 >::type r1; 132typedef <a href="./apply-wrap.html" class="identifier">apply_wrap</a><tt class="literal"><span class="pre">0</span></tt>< g0 >::type r2; 133typedef <a href="./apply-wrap.html" class="identifier">apply_wrap</a><tt class="literal"><span class="pre">2</span></tt>< f2,int,char >::type r3; 134 135<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same<r1,char> )); 136<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same<r2,char> )); 137<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same<r3,char> )); 138</pre> 139</div> 140<div class="section" id="id900"> 141<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> 142<p><a class="reference internal" href="./metafunctions.html">Metafunctions</a>, <a class="reference internal" href="./invocation.html">invocation</a>, <a class="reference internal" href="./apply.html">apply</a>, <a class="reference internal" href="./lambda.html">lambda</a>, <a class="reference internal" href="./quote.html">quote</a>, <a class="reference internal" href="./bind.html">bind</a>, <a class="reference internal" href="./protect.html">protect</a></p> 143<!-- Metafunctions/Invocation//unpack_args |30 --> 144</div> 145</div> 146 147<div class="footer-separator"></div> 148<table class="footer"><tr class="footer"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./apply.html" class="navigation-link">Prev</a> <a href="./unpack-args.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./apply.html" class="navigation-link">Back</a> <a href="./unpack-args.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./invocation.html" class="navigation-link">Up</a> <a href="../refmanual.html" class="navigation-link">Home</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./refmanual_toc.html" class="navigation-link">Full TOC</a></span></td> 149<td><div class="copyright-footer"><div class="copyright">Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams</div> 150Distributed under the Boost Software License, Version 1.0. (See accompanying 151file LICENSE_1_0.txt or copy at <a class="reference external" href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)</div></td></tr></table></body> 152</html> 153