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| 7 | <title>The MPL Reference Manual: Reversible Algorithm</title> |
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| 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> |
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| 13 | </tr></table><div class="header-separator"></div> |
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| 14 | <div class="section" id="reversible-algorithm"> |
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| 15 | <h1><a class="toc-backref" href="./algorithms-concepts.html#id391" name="reversible-algorithm">Reversible Algorithm</a></h1> |
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| 16 | <div class="section" id="reversible-description"> |
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| 17 | <h3><a class="subsection-title" href="#description" name="description">Description</a></h3> |
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| 18 | <p>A <a class="reference" href="./reversible-algorithm.html">Reversible Algorithm</a> is a member of a pair of |
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| 19 | transformation algorithms that iterate over their input sequence(s) |
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| 20 | in opposite directions. For each reversible |
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| 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>, |
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| 22 | that exhibits the exact semantics of <tt class="literal"><span class="pre">x</span></tt> except that the elements |
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| 23 | of its input sequence argument(s) are processed in the reverse |
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| 24 | order.</p> |
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| 25 | </div> |
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| 26 | <div class="section" id="reversible-expression-requirements"> |
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| 27 | <h3><a class="subsection-title" href="#expression-requirements" name="expression-requirements">Expression requirements</a></h3> |
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| 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 |
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| 29 | <a class="reference" 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 |
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| 30 | <a class="reference" href="./forward-sequence.html">Forward Sequence</a>s, and <tt class="literal"><span class="pre">in</span></tt> is an <a class="reference" href="./inserter.html">Inserter</a>.</p> |
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| 31 | <table border="1" class="table"> |
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| 32 | <colgroup> |
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| 33 | <col width="48%" /> |
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| 34 | <col width="28%" /> |
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| 35 | <col width="23%" /> |
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| 36 | </colgroup> |
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| 37 | <thead valign="bottom"> |
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| 38 | <tr><th>Expression</th> |
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| 39 | <th>Type</th> |
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| 40 | <th>Complexity</th> |
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| 41 | </tr> |
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| 42 | </thead> |
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| 43 | <tbody valign="top"> |
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| 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> |
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| 45 | <td><a class="reference" href="./forward-sequence.html">Forward Sequence</a></td> |
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| 46 | <td>Unspecified.</td> |
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| 47 | </tr> |
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| 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> |
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| 49 | <td>Any type</td> |
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| 50 | <td>Unspecified.</td> |
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| 51 | </tr> |
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| 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> |
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| 53 | <td><a class="reference" href="./forward-sequence.html">Forward Sequence</a></td> |
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| 54 | <td>Unspecified.</td> |
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| 55 | </tr> |
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| 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> |
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| 57 | <td>Any type</td> |
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| 58 | <td>Unspecified.</td> |
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| 59 | </tr> |
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| 60 | </tbody> |
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| 61 | </table> |
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| 62 | </div> |
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| 63 | <div class="section" id="reversible-expression-semantics"> |
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| 64 | <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> |
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| 65 | <pre class="literal-block"> |
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| 66 | typedef x<<em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,...<em>s</em><sub>n</sub>,...>::type t; |
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| 67 | </pre> |
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| 68 | <table class="field-list" frame="void" rules="none"> |
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| 69 | <col class="field-name" /> |
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| 70 | <col class="field-body" /> |
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| 71 | <tbody valign="top"> |
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| 72 | <tr class="field"><th class="field-name">Precondition:</th><td class="field-body"><em>s</em><sub>1</sub> is an <a class="reference" href="./extensible-sequence.html">Extensible Sequence</a>.</td> |
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| 73 | </tr> |
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| 74 | <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> |
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| 75 | <pre class="literal-block"> |
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| 76 | x< |
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| 77 | <em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,...<em>s</em><sub>n</sub>,... |
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| 78 | , <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 > |
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| 79 | >::type |
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| 80 | </pre> |
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| 81 | <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> |
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| 82 | <pre class="literal-block"> |
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| 83 | reverse_x< |
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| 84 | <em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,...<em>s</em><sub>n</sub>,... |
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| 85 | , <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 > |
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| 86 | >::type |
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| 87 | </pre> |
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| 88 | <p class="last">otherwise.</p> |
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| 89 | </td> |
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| 90 | </tr> |
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| 91 | </tbody> |
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| 92 | </table> |
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| 93 | <!-- .......................................................................... --> |
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| 94 | <pre class="literal-block"> |
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| 95 | typedef x<<em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,...<em>s</em><sub>n</sub>,...in>::type t; |
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| 96 | </pre> |
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| 97 | <table class="field-list" frame="void" rules="none"> |
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| 98 | <col class="field-name" /> |
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| 99 | <col class="field-body" /> |
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| 100 | <tbody valign="top"> |
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| 101 | <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 |
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| 102 | <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> |
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| 103 | </tr> |
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| 104 | </tbody> |
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| 105 | </table> |
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| 106 | <!-- .......................................................................... --> |
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| 107 | <pre class="literal-block"> |
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| 108 | typedef reverse_x<<em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,... <em>s</em><sub>n</sub>,... >::type t; |
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| 109 | </pre> |
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| 110 | <table class="field-list" frame="void" rules="none"> |
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| 111 | <col class="field-name" /> |
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| 112 | <col class="field-body" /> |
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| 113 | <tbody valign="top"> |
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| 114 | <tr class="field"><th class="field-name">Precondition:</th><td class="field-body"><em>s</em><sub>1</sub> is an <a class="reference" href="./extensible-sequence.html">Extensible Sequence</a>.</td> |
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| 115 | </tr> |
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| 116 | <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> |
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| 117 | <pre class="literal-block"> |
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| 118 | x< |
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| 119 | <em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,...<em>s</em><sub>n</sub>,... |
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| 120 | , <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 > |
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| 121 | >::type |
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| 122 | </pre> |
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| 123 | <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> |
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| 124 | <pre class="literal-block"> |
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| 125 | reverse_x< |
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| 126 | <em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,...<em>s</em><sub>n</sub>,... |
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| 127 | , <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 > |
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| 128 | >::type |
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| 129 | </pre> |
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| 130 | <p class="last">otherwise.</p> |
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| 131 | </td> |
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| 132 | </tr> |
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| 133 | </tbody> |
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| 134 | </table> |
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| 135 | <!-- .......................................................................... --> |
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| 136 | <pre class="literal-block"> |
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| 137 | typedef reverse_x<<em>s</em><sub>1</sub>,<em>s</em><sub>2</sub>,...<em>s</em><sub>n</sub>,... in>::type t; |
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| 138 | </pre> |
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| 139 | <table class="field-list" frame="void" rules="none"> |
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| 140 | <col class="field-name" /> |
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| 141 | <col class="field-body" /> |
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| 142 | <tbody valign="top"> |
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| 143 | <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 |
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| 144 | <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> |
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| 145 | </tr> |
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| 146 | </tbody> |
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| 147 | </table> |
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| 148 | </div> |
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| 149 | <div class="section" id="reversible-example"> |
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| 150 | <h3><a class="subsection-title" href="#example" name="example">Example</a></h3> |
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| 151 | <pre class="literal-block"> |
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| 152 | typedef <a href="./transform.html" class="identifier">transform</a>< |
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| 153 | <a href="./range-c.html" class="identifier">range_c</a><int,0,10> |
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| 154 | , <a href="./plus.html" class="identifier">plus</a><_1,<a href="./int.html" class="identifier">int_</a><7> > |
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| 155 | , <a href="./back-inserter.html" class="identifier">back_inserter</a>< vector0<> > |
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| 156 | >::type r1; |
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| 157 | |
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| 158 | typedef <a href="./transform.html" class="identifier">transform</a>< r1, <a href="./minus.html" class="identifier">minus</a><_1,<a href="./int.html" class="identifier">int_</a><2> > >::type r2; |
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| 159 | typedef <a href="./reverse-transform.html" class="identifier">reverse_transform</a>< |
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| 160 | r2 |
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| 161 | , <a href="./minus.html" class="identifier">minus</a><_1,5> |
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| 162 | , <a href="./front-inserter.html" class="identifier">front_inserter</a>< vector0<> > |
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| 163 | >::type r3; |
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| 164 | |
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| 165 | <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> > )); |
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| 166 | <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> > )); |
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| 167 | <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> > )); |
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| 168 | </pre> |
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| 169 | </div> |
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| 170 | <div class="section" id="reversible-models"> |
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| 171 | <h3><a class="subsection-title" href="#models" name="models">Models</a></h3> |
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| 172 | <ul class="simple"> |
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| 173 | <li><a class="refentry reference" href="./transform.html"><tt class="refentry literal"><span class="pre">transform</span></tt></a></li> |
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| 174 | <li><a class="refentry reference" href="./remove.html"><tt class="refentry literal"><span class="pre">remove</span></tt></a></li> |
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| 175 | <li><a class="refentry reference" href="./replace.html"><tt class="refentry literal"><span class="pre">replace</span></tt></a></li> |
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| 176 | </ul> |
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| 177 | </div> |
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| 178 | <div class="section" id="reversible-see-also"> |
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| 179 | <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> |
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| 180 | <p><a class="reference" href="./transformation-algorithms.html">Transformation Algorithms</a>, <a class="reference" href="./inserter.html">Inserter</a></p> |
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| 181 | <!-- modtime: November 13, 2004 01:42:46 +0000 --> |
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| 182 | </div> |
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