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| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_bimap.the_tutorial.unconstrained_sets"></a><a class="link" href="unconstrained_sets.html" title="Unconstrained Sets">Unconstrained |
| Sets</a> |
| </h3></div></div></div> |
| <p> |
| Unconstrained sets allow the user to disable one of the views of a bimap. |
| Doing so makes the bimap operations execute faster and reduces memory consumption. |
| This completes the bidirectional mapping framework by including unidirectional |
| mappings as a particular case. |
| </p> |
| <p> |
| Unconstrained sets are useful for the following reasons: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| A bimap type has stronger guarantees than its standard equivalent, and |
| includes some useful functions (replace, modify) that the standard does |
| not have. |
| </li> |
| <li class="listitem"> |
| You can view the mapping as a collection of relations. |
| </li> |
| <li class="listitem"> |
| Using this kind of map makes the code very extensible. If, at any moment |
| of the development, the need to perform searches from the right side |
| of the mapping arises, the only necessary change is to the <code class="computeroutput"><span class="keyword">typedef</span></code>. |
| </li> |
| </ul></div> |
| <p> |
| Given this bimap instance, |
| </p> |
| <p> |
| |
| </p> |
| <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> |
| <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> |
| |
| <span class="identifier">bm_type</span> <span class="identifier">bm</span><span class="special">;</span> |
| <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> |
| </pre> |
| <p> |
| </p> |
| <p> |
| or this standard map one |
| </p> |
| <p> |
| |
| </p> |
| <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> |
| |
| <span class="identifier">map_type</span> <span class="identifier">m</span><span class="special">;</span> |
| </pre> |
| <p> |
| </p> |
| <p> |
| The following code snippet is valid |
| </p> |
| <p> |
| |
| </p> |
| <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> |
| |
| <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> |
| |
| <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> |
| <span class="special">{</span> |
| <a class="co" name="boost_bimap14co" href="unconstrained_sets.html#boost_bimap14"><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> |
| <span class="special">}</span> |
| |
| <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> |
| </pre> |
| <p> |
| </p> |
| <p> |
| </p> |
| <div class="calloutlist"><table border="0" summary="Callout list"><tr> |
| <td width="5%" valign="top" align="left"><p><a name="boost_bimap14"></a><a href="#boost_bimap14co"><img src="../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a> </p></td> |
| <td valign="top" align="left"><p> The right collection of the bimap is mutable so its elements can be modified |
| using iterators. </p></td> |
| </tr></table></div> |
| <p> |
| </p> |
| <p> |
| But using a bimap has some benefits |
| </p> |
| <p> |
| |
| </p> |
| <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> |
| <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> |
| |
| <a class="co" name="boost_bimap15co" href="unconstrained_sets.html#boost_bimap15"><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> |
| <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> |
| <span class="special">{</span> |
| <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> |
| <span class="special">}</span> |
| |
| <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> |
| </pre> |
| <p> |
| </p> |
| <p> |
| </p> |
| <div class="calloutlist"><table border="0" summary="Callout list"><tr> |
| <td width="5%" valign="top" align="left"><p><a name="boost_bimap15"></a><a href="#boost_bimap15co"><img src="../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a> </p></td> |
| <td valign="top" align="left"><p> This range is a model of BidirectionalRange, read the docs of Boost.Range |
| for more information. </p></td> |
| </tr></table></div> |
| <p> |
| </p> |
| <p> |
| <a href="../../../../example/unconstrained_collection.cpp" target="_top">Go to source code</a> |
| </p> |
| </div> |
| <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> |
| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2006 -2007 Matias Capeletto<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| 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>) |
| </p> |
| </div></td> |
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