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| 4 | <title>Unconstrained Sets</title> | |
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| 24 | </div> | |
| 25 | <div class="section boost_bimap_the_tutorial_unconstrained_sets"> | |
| 26 | <div class="titlepage"><div><div><h3 class="title"> | |
| 27 | <a name="boost_bimap.the_tutorial.unconstrained_sets"></a><a class="link" href="unconstrained_sets.html" title="Unconstrained Sets">Unconstrained | |
| 28 | Sets</a> | |
| 29 | </h3></div></div></div> | |
| 30 | <p> | |
| 31 | Unconstrained sets allow the user to disable one of the views of a bimap. | |
| 32 | Doing so makes the bimap operations execute faster and reduces memory consumption. | |
| 33 | This completes the bidirectional mapping framework by including unidirectional | |
| 34 | mappings as a particular case. | |
| 35 | </p> | |
| 36 | <p> | |
| 37 | Unconstrained sets are useful for the following reasons: | |
| 38 | </p> | |
| 39 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
| 40 | <li class="listitem"> | |
| 41 | A bimap type has stronger guarantees than its standard equivalent, and | |
| 42 | includes some useful functions (replace, modify) that the standard does | |
| 43 | not have. | |
| 44 | </li> | |
| 45 | <li class="listitem"> | |
| 46 | You can view the mapping as a collection of relations. | |
| 47 | </li> | |
| 48 | <li class="listitem"> | |
| 49 | Using this kind of map makes the code very extensible. If, at any moment | |
| 50 | of the development, the need to perform searches from the right side | |
| 51 | of the mapping arises, the only necessary change is to the <code class="computeroutput"><span class="keyword">typedef</span></code>. | |
| 52 | </li> | |
| 53 | </ul></div> | |
| 54 | <p> | |
| 55 | Given this bimap instance, | |
| 56 | </p> | |
| 57 | <p> | |
| 58 | </p> | |
| 59 | <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">bimap</span><span class="special"><</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">,</span> <span class="identifier">unconstrained_set_of</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="special">></span> <span class="identifier">bm_type</span><span class="special">;</span> | |
| 60 | <span class="keyword">typedef</span> <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">left_map</span> <span class="identifier">map_type</span><span class="special">;</span> | |
| 61 | ||
| 62 | <span class="identifier">bm_type</span> <span class="identifier">bm</span><span class="special">;</span> | |
| 63 | <span class="identifier">map_type</span> <span class="special">&</span> <span class="identifier">m</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">;</span> | |
| 64 | </pre> | |
| 65 | <p> | |
| 66 | </p> | |
| 67 | <p> | |
| 68 | or this standard map one | |
| 69 | </p> | |
| 70 | <p> | |
| 71 | </p> | |
| 72 | <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">map</span><span class="special"><</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">,</span> <span class="keyword">int</span> <span class="special">></span> <span class="identifier">map_type</span><span class="special">;</span> | |
| 73 | ||
| 74 | <span class="identifier">map_type</span> <span class="identifier">m</span><span class="special">;</span> | |
| 75 | </pre> | |
| 76 | <p> | |
| 77 | </p> | |
| 78 | <p> | |
| 79 | The following code snippet is valid | |
| 80 | </p> | |
| 81 | <p> | |
| 82 | </p> | |
| 83 | <pre class="programlisting"><span class="identifier">m</span><span class="special">[</span><span class="string">"one"</span><span class="special">]</span> <span class="special">=</span> <span class="number">1</span><span class="special">;</span> | |
| 84 | ||
| 85 | <span class="identifier">assert</span><span class="special">(</span> <span class="identifier">m</span><span class="special">.</span><span class="identifier">find</span><span class="special">(</span><span class="string">"one"</span><span class="special">)</span> <span class="special">!=</span> <span class="identifier">m</span><span class="special">.</span><span class="identifier">end</span><span class="special">()</span> <span class="special">);</span> | |
| 86 | ||
| 87 | <span class="keyword">for</span><span class="special">(</span> <span class="identifier">map_type</span><span class="special">::</span><span class="identifier">iterator</span> <span class="identifier">i</span> <span class="special">=</span> <span class="identifier">m</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">iend</span> <span class="special">=</span> <span class="identifier">m</span><span class="special">.</span><span class="identifier">end</span><span class="special">();</span> <span class="identifier">i</span> <span class="special">!=</span> <span class="identifier">iend</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span> <span class="special">)</span> | |
| 88 | <span class="special">{</span> | |
| 89 | <a class="co" name="boost_bimap.the_tutorial.unconstrained_sets.c0" href="unconstrained_sets.html#boost_bimap.the_tutorial.unconstrained_sets.c1"><img src="../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a><span class="special">++(</span><span class="identifier">i</span><span class="special">-></span><span class="identifier">second</span><span class="special">);</span> | |
| 90 | <span class="special">}</span> | |
| 91 | ||
| 92 | <span class="identifier">m</span><span class="special">.</span><span class="identifier">erase</span><span class="special">(</span><span class="string">"one"</span><span class="special">);</span> | |
| 93 | </pre> | |
| 94 | <p> | |
| 95 | </p> | |
| 96 | <div class="calloutlist"><table border="0" summary="Callout list"><tr> | |
| 97 | <td width="5%" valign="top" align="left"><p><a name="boost_bimap.the_tutorial.unconstrained_sets.c1"></a><a href="#boost_bimap.the_tutorial.unconstrained_sets.c0"><img src="../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a> </p></td> | |
| 98 | <td valign="top" align="left"><p> | |
| 99 | The right collection of the bimap is mutable so its elements can be modified | |
| 100 | using iterators. | |
| 101 | </p></td> | |
| 102 | </tr></table></div> | |
| 103 | <p> | |
| 104 | But using a bimap has some benefits | |
| 105 | </p> | |
| 106 | <p> | |
| 107 | </p> | |
| 108 | <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">map_type</span><span class="special">::</span><span class="identifier">const_iterator</span> <span class="identifier">const_iterator</span><span class="special">;</span> | |
| 109 | <span class="keyword">typedef</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">const_iterator</span><span class="special">,</span><span class="identifier">const_iterator</span><span class="special">></span> <span class="identifier">const_range</span><span class="special">;</span> | |
| 110 | ||
| 111 | <a class="co" name="boost_bimap.the_tutorial.unconstrained_sets.c2" href="unconstrained_sets.html#boost_bimap.the_tutorial.unconstrained_sets.c3"><img src="../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a><span class="identifier">const_range</span> <span class="identifier">r</span> <span class="special">=</span> <span class="identifier">m</span><span class="special">.</span><span class="identifier">range</span><span class="special">(</span> <span class="string">"one"</span> <span class="special"><=</span> <span class="identifier">_key</span><span class="special">,</span> <span class="identifier">_key</span> <span class="special"><=</span> <span class="string">"two"</span> <span class="special">);</span> | |
| 112 | <span class="keyword">for</span><span class="special">(</span> <span class="identifier">const_iterator</span> <span class="identifier">i</span> <span class="special">=</span> <span class="identifier">r</span><span class="special">.</span><span class="identifier">first</span><span class="special">;</span> <span class="identifier">i</span> <span class="special">!=</span> <span class="identifier">r</span><span class="special">.</span><span class="identifier">second</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span> <span class="special">)</span> | |
| 113 | <span class="special">{</span> | |
| 114 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">i</span><span class="special">-></span><span class="identifier">first</span> <span class="special"><<</span> <span class="string">"-->"</span> <span class="special"><<</span> <span class="identifier">i</span><span class="special">-></span><span class="identifier">second</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> | |
| 115 | <span class="special">}</span> | |
| 116 | ||
| 117 | <span class="identifier">m</span><span class="special">.</span><span class="identifier">modify_key</span><span class="special">(</span> <span class="identifier">m</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">_key</span> <span class="special">=</span> <span class="string">"1"</span> <span class="special">);</span> | |
| 118 | </pre> | |
| 119 | <p> | |
| 120 | </p> | |
| 121 | <div class="calloutlist"><table border="0" summary="Callout list"><tr> | |
| 122 | <td width="5%" valign="top" align="left"><p><a name="boost_bimap.the_tutorial.unconstrained_sets.c3"></a><a href="#boost_bimap.the_tutorial.unconstrained_sets.c2"><img src="../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a> </p></td> | |
| 123 | <td valign="top" align="left"><p> | |
| 124 | This range is a model of BidirectionalRange, read the docs of Boost.Range | |
| 125 | for more information. | |
| 126 | </p></td> | |
| 127 | </tr></table></div> | |
| 128 | <p> | |
| 129 | <a href="../../../../example/unconstrained_collection.cpp" target="_top">Go to source code</a> | |
| 130 | </p> | |
| 131 | </div> | |
| 132 | <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> | |
| 133 | <td align="left"></td> | |
| 134 | <td align="right"><div class="copyright-footer">Copyright © 2006-2012 Matias Capeletto<p> | |
| 135 | Distributed under the Boost Software License, Version 1.0. (See accompanying | |
| 136 | file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) | |
| 137 | </p> | |
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