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7<title>The MPL Reference Manual: reverse_iter_fold</title>
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11<table class="header"><tr class="header"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./reverse-fold.html" class="navigation-link">Prev</a>&nbsp;<a href="./accumulate.html" class="navigation-link">Next</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./reverse-fold.html" class="navigation-link">Back</a>&nbsp;<a href="./accumulate.html" class="navigation-link">Along</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</span><span class="navigation-group"><a href="./iteration-algorithms.html" class="navigation-link">Up</a>&nbsp;<a href="../refmanual.html" class="navigation-link">Home</a></span><span class="navigation-group-separator">&nbsp;|&nbsp;</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-iter-fold.html" class="navigation-link">reverse_iter_fold</a></td>
13</tr></table><div class="header-separator"></div>
14<div class="section" id="reverse-iter-fold">
15<h1><a class="toc-backref" href="./iteration-algorithms.html#id400" name="reverse-iter-fold">reverse_iter_fold</a></h1>
16<div class="section" id="iteration-reverse-synopsis">
17<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
18<pre class="literal-block">
19template&lt;
20      typename Sequence
21    , typename State
22    , typename BackwardOp
23    , typename ForwardOp = _1
24    &gt;
25struct <a href="./reverse-iter-fold.html" class="identifier">reverse_iter_fold</a>
26{
27    typedef <em>unspecified</em>  type;
28};
29</pre>
30</div>
31<div class="section" id="iteration-reverse-description">
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 each iterator in the range [<tt class="literal"><span class="pre"><a href="./begin.html" class="identifier">begin</a>&lt;Sequence&gt;::type</span></tt>, <tt class="literal"><span class="pre"><a href="./end.html" class="identifier">end</a>&lt;Sequence&gt;::type</span></tt>)
36in reverse order. If <tt class="literal"><span class="pre">ForwardOp</span></tt> is provided, then it's applied on forward
37traversal to form the result which is passed to the first <tt class="literal"><span class="pre">BackwardOp</span></tt> call.</p>
38</div>
39<div class="section" id="iteration-reverse-header">
40<h3><a class="subsection-title" href="#header" name="header">Header</a></h3>
41<pre class="literal-block">
42#include &lt;<a href="../../../../boost/mpl/reverse_iter_fold.hpp" class="header">boost/mpl/reverse_iter_fold.hpp</a>&gt;
43</pre>
44</div>
45<div class="section" id="algorithms-iteration-reverse-parameters">
46<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3>
47<table border="1" class="table">
48<colgroup>
49<col width="16%" />
50<col width="33%" />
51<col width="51%" />
52</colgroup>
53<thead valign="bottom">
54<tr><th>Parameter</th>
55<th>Requirement</th>
56<th>Description</th>
57</tr>
58</thead>
59<tbody valign="top">
60<tr><td><tt class="literal"><span class="pre">Sequence</span></tt></td>
61<td><a class="reference" href="./forward-sequence.html">Forward Sequence</a></td>
62<td>A sequence to iterate.</td>
63</tr>
64<tr><td><tt class="literal"><span class="pre">State</span></tt></td>
65<td>Any type</td>
66<td>The initial state for the first <tt class="literal"><span class="pre">BackwardOp</span></tt>
67/ <tt class="literal"><span class="pre">ForwardOp</span></tt> application.</td>
68</tr>
69<tr><td><tt class="literal"><span class="pre">BackwardOp</span></tt></td>
70<td>Binary <a class="reference" href="./lambda-expression.html">Lambda Expression</a></td>
71<td>The operation to be executed on backward
72traversal.</td>
73</tr>
74<tr><td><tt class="literal"><span class="pre">ForwardOp</span></tt></td>
75<td>Binary <a class="reference" href="./lambda-expression.html">Lambda Expression</a></td>
76<td>The operation to be executed on forward
77traversal.</td>
78</tr>
79</tbody>
80</table>
81</div>
82<div class="section" id="iteration-reverse-expression-semantics">
83<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
84<p>For any <a class="reference" href="./forward-sequence.html">Forward Sequence</a> <tt class="literal"><span class="pre">s</span></tt>, binary <a class="reference" 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>,
85and arbitrary type <tt class="literal"><span class="pre">state</span></tt>:</p>
86<pre class="literal-block">
87typedef <a href="./reverse-iter-fold.html" class="identifier">reverse_iter_fold</a>&lt; s,state,backward_op &gt;::type t;
88</pre>
89<table class="field-list" frame="void" rules="none">
90<col class="field-name" />
91<col class="field-body" />
92<tbody valign="top">
93<tr class="field"><th class="field-name">Return type:</th><td class="field-body">A type.</td>
94</tr>
95<tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p>
96<pre class="literal-block">
97typedef <a href="./begin.html" class="identifier">begin</a>&lt;s&gt;::type i<sub>1</sub>;
98typedef <a href="./next.html" class="identifier">next</a>&lt;i<sub>1</sub>&gt;::type i<sub>2</sub>;
99<em>...</em>
100typedef <a href="./next.html" class="identifier">next</a>&lt;i<sub>n</sub>&gt;::type last;
101typedef <a href="./apply.html" class="identifier">apply</a>&lt;backward_op,state,i<sub>n</sub>&gt;::type state<sub>n</sub>;
102typedef <a href="./apply.html" class="identifier">apply</a>&lt;backward_op,state<sub>n</sub>,i<sub>n-1</sub>&gt;::type state<sub>n-1</sub>;
103<em>...</em>
104typedef <a href="./apply.html" class="identifier">apply</a>&lt;backward_op,state<sub>2</sub>,i<sub>1</sub>&gt;::type state<sub>1</sub>;
105typedef state<sub>1</sub> t;
106</pre>
107<p class="last">where <tt class="literal"><span class="pre">n</span> <span class="pre">==</span> <span class="pre"><a href="./size.html" class="identifier">size</a>&lt;s&gt;::value</span></tt> and <tt class="literal"><span class="pre">last</span></tt> is identical to <tt class="literal"><span class="pre"><a href="./end.html" class="identifier">end</a>&lt;s&gt;::type</span></tt>; equivalent
108to <tt class="literal"><span class="pre">typedef</span> <span class="pre">state</span> <span class="pre">t;</span></tt> if <tt class="literal"><span class="pre"><a href="./empty.html" class="identifier">empty</a>&lt;s&gt;::value</span> <span class="pre">==</span> <span class="pre">true</span></tt>.</p>
109</td>
110</tr>
111</tbody>
112</table>
113<!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
114<pre class="literal-block">
115typedef <a href="./reverse-iter-fold.html" class="identifier">reverse_iter_fold</a>&lt; s,state,backward_op,forward_op &gt;::type t;
116</pre>
117<table class="field-list" frame="void" rules="none">
118<col class="field-name" />
119<col class="field-body" />
120<tbody valign="top">
121<tr class="field"><th class="field-name">Return type:</th><td class="field-body">A type.</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-iter-fold.html" class="identifier">reverse_iter_fold</a>&lt;
126      Sequence
127    , <a href="./iter-fold.html" class="identifier">iter_fold</a>&lt;s,state,forward_op&gt;::type
128    , backward_op
129    &gt;::type t;
130</pre>
131</td>
132</tr>
133</tbody>
134</table>
135</div>
136<div class="section" id="iteration-reverse-complexity">
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>&lt;s&gt;::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="iteration-reverse-example">
141<h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
142<p>Build a list of iterators to the negative elements in a sequence.</p>
143<pre class="literal-block">
144typedef <a href="./vector-c.html" class="identifier">vector_c</a>&lt;int,5,-1,0,-7,-2,0,-5,4&gt; numbers;
145typedef <a href="./list-c.html" class="identifier">list_c</a>&lt;int,-1,-7,-2,-5&gt; negatives;
146typedef <a href="./reverse-iter-fold.html" class="identifier">reverse_iter_fold</a>&lt;
147      numbers
148    , <a href="./list.html" class="identifier">list</a>&lt;&gt;
149    , <a href="./if.html" class="identifier">if_</a>&lt; <a href="./less.html" class="identifier">less</a>&lt; <a href="./deref.html" class="identifier">deref</a>&lt;_2&gt;,<a href="./int.html" class="identifier">int_</a>&lt;0&gt; &gt;, <a href="./push-front.html" class="identifier">push_front</a>&lt;_1,_2&gt;, _1 &gt;
150    &gt;::type iters;
151
152<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./equal.html" class="identifier">equal</a>&lt; 
153      negatives
154    , <a href="./transform-view.html" class="identifier">transform_view</a>&lt; iters,<a href="./deref.html" class="identifier">deref</a>&lt;_1&gt; >
155    > ));
156</pre>
157</div>
158<div class="section" id="iteration-reverse-see-also">
159<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
160<p><a class="reference" href="./algorithms.html">Algorithms</a>, <a class="refentry reference" href="./iter-fold.html"><tt class="refentry literal"><span class="pre">iter_fold</span></tt></a>, <a class="refentry reference" href="./reverse-fold.html"><tt class="refentry literal"><span class="pre">reverse_fold</span></tt></a>, <a class="refentry reference" href="./fold.html"><tt class="refentry literal"><span class="pre">fold</span></tt></a></p>
161<!-- modtime: November 13, 2004 02:51:20 +0000 -->
162<!-- Algorithms/Iteration Algorithms//accumulate |10 -->
163</div>
164</div>
165
166<div class="footer-separator"></div>
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