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: reverse_fold</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="./iter-fold.html" class="navigation-link">Prev</a> <a href="./reverse-iter-fold.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./iter-fold.html" class="navigation-link">Back</a> <a href="./reverse-iter-fold.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./iteration-algorithms.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="./algorithms.html" class="navigation-link">Algorithms</a> / <a href="./iteration-algorithms.html" class="navigation-link">Iteration Algorithms</a> / <a href="./reverse-fold.html" class="navigation-link">reverse_fold</a></td> 13</tr></table><div class="header-separator"></div> 14<div class="section" id="reverse-fold"> 15<h1><a class="toc-backref" href="./iteration-algorithms.html#id1471">reverse_fold</a></h1> 16<div class="section" id="id509"> 17<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> 18<pre class="literal-block"> 19template< 20 typename Sequence 21 , typename State 22 , typename BackwardOp 23 , typename ForwardOp = <a href="./placeholders.html" class="identifier">_1</a> 24 > 25struct <a href="./reverse-fold.html" class="identifier">reverse_fold</a> 26{ 27 typedef <em>unspecified</em> type; 28}; 29</pre> 30</div> 31<div class="section" id="id510"> 32<h3><a class="subsection-title" href="#description" name="description">Description</a></h3> 33<p>Returns the result of the successive application of binary <tt class="literal"><span class="pre">BackwardOp</span></tt> to the 34result of the previous <tt class="literal"><span class="pre">BackwardOp</span></tt> invocation (<tt class="literal"><span class="pre">State</span></tt> if it's the first call) 35and every element in the range [<tt class="literal"><span class="pre"><a href="./begin.html" class="identifier">begin</a><Sequence>::type</span></tt>, <tt class="literal"><span class="pre"><a href="./end.html" class="identifier">end</a><Sequence>::type</span></tt>) in 36reverse order. If <tt class="literal"><span class="pre">ForwardOp</span></tt> is provided, then it is applied on forward 37traversal to form the result that is passed to the first <tt class="literal"><span class="pre">BackwardOp</span></tt> call.</p> 38</div> 39<div class="section" id="id511"> 40<h3><a class="subsection-title" href="#header" name="header">Header</a></h3> 41<pre class="literal-block"> 42#include <<a href="../../../../boost/mpl/reverse_fold.hpp" class="header">boost/mpl/reverse_fold.hpp</a>> 43</pre> 44</div> 45<div class="section" id="id512"> 46<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> 47</div> 48<div class="section" id="id513"> 49<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> 50<table border="1" class="docutils table"> 51<colgroup> 52<col width="16%" /> 53<col width="33%" /> 54<col width="51%" /> 55</colgroup> 56<thead valign="bottom"> 57<tr><th class="head">Parameter</th> 58<th class="head">Requirement</th> 59<th class="head">Description</th> 60</tr> 61</thead> 62<tbody valign="top"> 63<tr><td><tt class="literal"><span class="pre">Sequence</span></tt></td> 64<td><a class="reference internal" href="./forward-sequence.html">Forward Sequence</a></td> 65<td>A sequence to iterate.</td> 66</tr> 67<tr><td><tt class="literal"><span class="pre">State</span></tt></td> 68<td>Any type</td> 69<td>The initial state for the first <tt class="literal"><span class="pre">BackwardOp</span></tt> 70/ <tt class="literal"><span class="pre">ForwardOp</span></tt> application.</td> 71</tr> 72<tr><td><tt class="literal"><span class="pre">BackwardOp</span></tt></td> 73<td>Binary <a class="reference internal" href="./lambda-expression.html">Lambda Expression</a></td> 74<td>The operation to be executed on backward 75traversal.</td> 76</tr> 77<tr><td><tt class="literal"><span class="pre">ForwardOp</span></tt></td> 78<td>Binary <a class="reference internal" href="./lambda-expression.html">Lambda Expression</a></td> 79<td>The operation to be executed on forward 80traversal.</td> 81</tr> 82</tbody> 83</table> 84</div> 85<div class="section" id="id514"> 86<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> 87<p>For any <a class="reference internal" href="./forward-sequence.html">Forward Sequence</a> <tt class="literal"><span class="pre">s</span></tt>, binary <a class="reference internal" href="./lambda-expression.html">Lambda Expression</a> <tt class="literal"><span class="pre">backward_op</span></tt> and <tt class="literal"><span class="pre">forward_op</span></tt>, 88and arbitrary type <tt class="literal"><span class="pre">state</span></tt>:</p> 89<pre class="literal-block"> 90typedef <a href="./reverse-fold.html" class="identifier">reverse_fold</a>< s,state,backward_op >::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"><p class="first">A type</p> 97</td> 98</tr> 99<tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p> 100<pre class="last literal-block"> 101typedef <a href="./lambda.html" class="identifier">lambda</a><backward_op>::type op; 102typedef <a href="./reverse-iter-fold.html" class="identifier">reverse_iter_fold</a>< 103 s 104 , state 105 , apply_wrap2< op, <a href="./placeholders.html" class="identifier">_1</a>, <a href="./deref.html" class="identifier">deref</a><<a href="./placeholders.html" class="identifier">_2</a>> > 106 >::type t; 107</pre> 108</td> 109</tr> 110</tbody> 111</table> 112<!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ --> 113<pre class="literal-block"> 114typedef <a href="./reverse-fold.html" class="identifier">reverse_fold</a>< s,state,backward_op,forward_op >::type t; 115</pre> 116<table class="docutils field-list" frame="void" rules="none"> 117<col class="field-name" /> 118<col class="field-body" /> 119<tbody valign="top"> 120<tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first">A type.</p> 121</td> 122</tr> 123<tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p> 124<pre class="last literal-block"> 125typedef <a href="./reverse-fold.html" class="identifier">reverse_fold</a>< 126 Sequence 127 , <a href="./fold.html" class="identifier">fold</a><s,state,forward_op>::type 128 , backward_op 129 >::type t; 130</pre> 131</td> 132</tr> 133</tbody> 134</table> 135</div> 136<div class="section" id="id515"> 137<h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3> 138<p>Linear. Exactly <tt class="literal"><span class="pre"><a href="./size.html" class="identifier">size</a><s>::value</span></tt> applications of <tt class="literal"><span class="pre">backward_op</span></tt> and <tt class="literal"><span class="pre">forward_op</span></tt>.</p> 139</div> 140<div class="section" id="id516"> 141<h3><a class="subsection-title" href="#example" name="example">Example</a></h3> 142<p>Remove non-negative elements from a sequence <a class="footnote-reference" href="#reverse-fold-note" id="id517">[2]</a>.</p> 143<pre class="literal-block"> 144typedef <a href="./list-c.html" class="identifier">list_c</a><int,5,-1,0,-7,-2,0,-5,4> numbers; 145typedef <a href="./list-c.html" class="identifier">list_c</a><int,-1,-7,-2,-5> negatives; 146typedef <a href="./reverse-fold.html" class="identifier">reverse_fold</a>< 147 numbers 148 , <a href="./list-c.html" class="identifier">list_c</a><int> 149 , <a href="./if.html" class="identifier">if_</a>< <a href="./less.html" class="identifier">less</a>< <a href="./placeholders.html" class="identifier">_2</a>,<a href="./int.html" class="identifier">int_</a><0> >, <a href="./push-front.html" class="identifier">push_front</a><<a href="./placeholders.html" class="identifier">_1</a>,<a href="./placeholders.html" class="identifier">_2</a>,>, <a href="./placeholders.html" class="identifier">_1</a> > 150 >::type result; 151 152<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./equal.html" class="identifier">equal</a>< negatives,result > )); 153</pre> 154<table class="docutils footnote" frame="void" id="reverse-fold-note" rules="none"> 155<colgroup><col class="label" /><col /></colgroup> 156<tbody valign="top"> 157<tr><td class="label"><a class="fn-backref" href="#id517">[2]</a></td><td>See <tt class="literal"><span class="pre"><a href="./remove-if.html" class="identifier">remove_if</a></span></tt> for a more compact way to do this.</td></tr> 158</tbody> 159</table> 160</div> 161<div class="section" id="id518"> 162<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> 163<p><a class="reference internal" href="./algorithms.html">Algorithms</a>, <a class="reference internal" href="./fold.html">fold</a>, <a class="reference internal" href="./reverse-iter-fold.html">reverse_iter_fold</a>, <a class="reference internal" href="./iter-fold.html">iter_fold</a></p> 164<!-- Algorithms/Iteration Algorithms//reverse_iter_fold --> 165</div> 166</div> 167 168<div class="footer-separator"></div> 169<table class="footer"><tr class="footer"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./iter-fold.html" class="navigation-link">Prev</a> <a href="./reverse-iter-fold.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./iter-fold.html" class="navigation-link">Back</a> <a href="./reverse-iter-fold.html" class="navigation-link">Along</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./iteration-algorithms.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> 170<td><div class="copyright-footer"><div class="copyright">Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams</div> 171Distributed under the Boost Software License, Version 1.0. (See accompanying 172file 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> 173</html> 174