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: Reversible Algorithm</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="./inserter.html" class="navigation-link">Prev</a> <a href="./inserters.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./inserter.html" class="navigation-link">Back</a> Along</span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./algorithms-concepts.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="./algorithms-concepts.html" class="navigation-link">Concepts</a> / <a href="./reversible-algorithm.html" class="navigation-link">Reversible Algorithm</a></td> 13 </tr></table><div class="header-separator"></div> 14 <div class="section" id="reversible-algorithm"> 15 <h1><a class="toc-backref" href="./algorithms-concepts.html#id1463">Reversible Algorithm</a></h1> 16 <div class="section" id="id459"> 17 <h3><a class="subsection-title" href="#description" name="description">Description</a></h3> 18 <p>A <a class="reference internal" href="./reversible-algorithm.html">Reversible Algorithm</a> is a member of a pair of 19 transformation algorithms that iterate over their input sequence(s) 20 in opposite directions. For each reversible 21 algorithm <tt class="literal"><span class="pre">x</span></tt> there exists a <em>counterpart</em> algorithm <tt class="literal"><span class="pre">reverse_x</span></tt>, 22 that exhibits the exact semantics of <tt class="literal"><span class="pre">x</span></tt> except that the elements 23 of its input sequence argument(s) are processed in the reverse 24 order.</p> 25 </div> 26 <div class="section" id="id460"> 27 <h3><a class="subsection-title" href="#expression-requirements" name="expression-requirements">Expression requirements</a></h3> 28 <p>In the following table and subsequent specifications, <tt class="literal"><span class="pre">x</span></tt> is a placeholder token for the actual 29 <a class="reference internal" href="./reversible-algorithm.html">Reversible Algorithm</a>'s name, <em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,...<em>s</em><sub>n</sub> are 30 <a class="reference internal" href="./forward-sequence.html">Forward Sequence</a>s, and <tt class="literal"><span class="pre">in</span></tt> is an <a class="reference internal" href="./inserter.html">Inserter</a>.</p> 31 <table border="1" class="docutils table"> 32 <colgroup> 33 <col width="48%" /> 34 <col width="28%" /> 35 <col width="23%" /> 36 </colgroup> 37 <thead valign="bottom"> 38 <tr><th class="head">Expression</th> 39 <th class="head">Type</th> 40 <th class="head">Complexity</th> 41 </tr> 42 </thead> 43 <tbody valign="top"> 44 <tr><td><tt class="literal"><span class="pre">x<</span></tt><em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,...<em>s</em><sub>n</sub>, ...<tt class="literal"><span class="pre">>::type</span></tt></td> 45 <td><a class="reference internal" href="./forward-sequence.html">Forward Sequence</a></td> 46 <td>Unspecified.</td> 47 </tr> 48 <tr><td><tt class="literal"><span class="pre">x<</span></tt><em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,...<em>s</em><sub>n</sub>, ... <tt class="literal"><span class="pre">in>::type</span></tt></td> 49 <td>Any type</td> 50 <td>Unspecified.</td> 51 </tr> 52 <tr><td><tt class="literal"><span class="pre">reverse_x<</span></tt><em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,...<em>s</em><sub>n</sub>, ...<tt class="literal"><span class="pre">>::type</span></tt></td> 53 <td><a class="reference internal" href="./forward-sequence.html">Forward Sequence</a></td> 54 <td>Unspecified.</td> 55 </tr> 56 <tr><td><tt class="literal"><span class="pre">reverse_x<</span></tt><em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,...<em>s</em><sub>n</sub>, ... <tt class="literal"><span class="pre">in>::type</span></tt></td> 57 <td>Any type</td> 58 <td>Unspecified.</td> 59 </tr> 60 </tbody> 61 </table> 62 </div> 63 <div class="section" id="id461"> 64 <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> 65 <pre class="literal-block"> 66 typedef x<<em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,...<em>s</em><sub>n</sub>,...>::type t; 67 </pre> 68 <table class="docutils field-list" frame="void" rules="none"> 69 <col class="field-name" /> 70 <col class="field-body" /> 71 <tbody valign="top"> 72 <tr class="field"><th class="field-name">Precondition:</th><td class="field-body"><p class="first"><em>s</em><sub>1</sub> is an <a class="reference internal" href="./extensible-sequence.html">Extensible Sequence</a>.</p> 73 </td> 74 </tr> 75 <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first"><tt class="literal"><span class="pre">t</span></tt> is equivalent to</p> 76 <pre class="literal-block"> 77 x< 78 <em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,...<em>s</em><sub>n</sub>,... 79 , <a href="./back-inserter.html" class="identifier">back_inserter</a>< <a href="./clear.html" class="identifier">clear</a><<em>s</em><sub>1</sub>>::type > 80 >::type 81 </pre> 82 <p>if <tt class="literal"><span class="pre">has_push_back<</span></tt><em>s</em><sub>1</sub><tt class="literal"><span class="pre">>::value</span> <span class="pre">==</span> <span class="pre">true</span></tt> and</p> 83 <pre class="literal-block"> 84 reverse_x< 85 <em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,...<em>s</em><sub>n</sub>,... 86 , <a href="./front-inserter.html" class="identifier">front_inserter</a>< <a href="./clear.html" class="identifier">clear</a><<em>s</em><sub>1</sub>>::type > 87 >::type 88 </pre> 89 <p class="last">otherwise.</p> 90 </td> 91 </tr> 92 </tbody> 93 </table> 94 <!-- .......................................................................... --> 95 <pre class="literal-block"> 96 typedef x<<em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,...<em>s</em><sub>n</sub>,...in>::type t; 97 </pre> 98 <table class="docutils field-list" frame="void" rules="none"> 99 <col class="field-name" /> 100 <col class="field-body" /> 101 <tbody valign="top"> 102 <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><tt class="literal"><span class="pre">t</span></tt> is the result of an <tt class="literal"><span class="pre">x</span></tt> invocation with arguments 103 <em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,... <em>s</em><sub>n</sub>,...<tt class="literal"><span class="pre">in</span></tt>.</td> 104 </tr> 105 </tbody> 106 </table> 107 <!-- .......................................................................... --> 108 <pre class="literal-block"> 109 typedef reverse_x<<em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,... <em>s</em><sub>n</sub>,... >::type t; 110 </pre> 111 <table class="docutils field-list" frame="void" rules="none"> 112 <col class="field-name" /> 113 <col class="field-body" /> 114 <tbody valign="top"> 115 <tr class="field"><th class="field-name">Precondition:</th><td class="field-body"><p class="first"><em>s</em><sub>1</sub> is an <a class="reference internal" href="./extensible-sequence.html">Extensible Sequence</a>.</p> 116 </td> 117 </tr> 118 <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first"><tt class="literal"><span class="pre">t</span></tt> is equivalent to</p> 119 <pre class="literal-block"> 120 x< 121 <em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,...<em>s</em><sub>n</sub>,... 122 , <a href="./front-inserter.html" class="identifier">front_inserter</a>< <a href="./clear.html" class="identifier">clear</a><<em>s</em><sub>1</sub>>::type > 123 >::type 124 </pre> 125 <p>if <tt class="literal"><span class="pre">has_push_front<</span></tt><em>s</em><sub>1</sub><tt class="literal"><span class="pre">>::value</span> <span class="pre">==</span> <span class="pre">true</span></tt> and</p> 126 <pre class="literal-block"> 127 reverse_x< 128 <em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,...<em>s</em><sub>n</sub>,... 129 , <a href="./back-inserter.html" class="identifier">back_inserter</a>< <a href="./clear.html" class="identifier">clear</a><<em>s</em><sub>1</sub>>::type > 130 >::type 131 </pre> 132 <p class="last">otherwise.</p> 133 </td> 134 </tr> 135 </tbody> 136 </table> 137 <!-- .......................................................................... --> 138 <pre class="literal-block"> 139 typedef reverse_x<<em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,...<em>s</em><sub>n</sub>,... in>::type t; 140 </pre> 141 <table class="docutils field-list" frame="void" rules="none"> 142 <col class="field-name" /> 143 <col class="field-body" /> 144 <tbody valign="top"> 145 <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><tt class="literal"><span class="pre">t</span></tt> is the result of a <tt class="literal"><span class="pre">reverse_x</span></tt> invocation with arguments 146 <em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,...<em>s</em><sub>n</sub>,...<tt class="literal"><span class="pre">in</span></tt>.</td> 147 </tr> 148 </tbody> 149 </table> 150 </div> 151 <div class="section" id="id462"> 152 <h3><a class="subsection-title" href="#example" name="example">Example</a></h3> 153 <pre class="literal-block"> 154 typedef <a href="./transform.html" class="identifier">transform</a>< 155 <a href="./range-c.html" class="identifier">range_c</a><int,0,10> 156 , <a href="./plus.html" class="identifier">plus</a><<a href="./placeholders.html" class="identifier">_1</a>,<a href="./int.html" class="identifier">int_</a><7> > 157 , <a href="./back-inserter.html" class="identifier">back_inserter</a>< vector0<> > 158 >::type r1; 159 160 typedef <a href="./transform.html" class="identifier">transform</a>< r1, <a href="./minus.html" class="identifier">minus</a><<a href="./placeholders.html" class="identifier">_1</a>,<a href="./int.html" class="identifier">int_</a><2> > >::type r2; 161 typedef <a href="./reverse-transform.html" class="identifier">reverse_transform</a>< 162 r2 163 , <a href="./minus.html" class="identifier">minus</a><<a href="./placeholders.html" class="identifier">_1</a>,5> 164 , <a href="./front-inserter.html" class="identifier">front_inserter</a>< vector0<> > 165 >::type r3; 166 167 <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./equal.html" class="identifier">equal</a><r1, <a href="./range-c.html" class="identifier">range_c</a><int,7,17> > )); 168 <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./equal.html" class="identifier">equal</a><r2, <a href="./range-c.html" class="identifier">range_c</a><int,5,15> > )); 169 <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./equal.html" class="identifier">equal</a><r3, <a href="./range-c.html" class="identifier">range_c</a><int,0,10> > )); 170 </pre> 171 </div> 172 <div class="section" id="id463"> 173 <h3><a class="subsection-title" href="#models" name="models">Models</a></h3> 174 <ul class="simple"> 175 <li><a class="reference internal" href="./transform.html">transform</a></li> 176 <li><a class="reference internal" href="./remove.html">remove</a></li> 177 <li><a class="reference internal" href="./replace.html">replace</a></li> 178 </ul> 179 </div> 180 <div class="section" id="id464"> 181 <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> 182 <p><a class="reference internal" href="./transformation-algorithms.html">Transformation Algorithms</a>, <a class="reference internal" href="./inserter.html">Inserter</a></p> 183 </div> 184 </div> 185 186 <div class="footer-separator"></div> 187 <table class="footer"><tr class="footer"><td class="header-group navigation-bar"><span class="navigation-group"><a href="./inserter.html" class="navigation-link">Prev</a> <a href="./inserters.html" class="navigation-link">Next</a></span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./inserter.html" class="navigation-link">Back</a> Along</span><span class="navigation-group-separator"> | </span><span class="navigation-group"><a href="./algorithms-concepts.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> 188 <td><div class="copyright-footer"><div class="copyright">Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams</div> 189 Distributed under the Boost Software License, Version 1.0. (See accompanying 190 file 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> 191 </html> 192