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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="move.move_and_containers"></a><a class="link" href="move_and_containers.html" title="Containers and move semantics">Containers and move semantics</a>
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</h2></div></div></div>
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<p>
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Movable but non-copyable types can be safely inserted into containers and movable
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and copyable types are more efficiently handled if those containers internally
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use move semantics instead of copy semantics. If the container needs to "change
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the location" of an element internally (e.g. vector reallocation) it will
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move the element instead of copying it. <span class="bold"><strong>Boost.Container</strong></span>
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containers are move-aware so you can write the following:
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<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">container</span><span class="special">/</span><span class="identifier">vector</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
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<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">cassert</span><span class="special">></span>
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<span class="comment">//Remember: 'file_descriptor' is NOT copyable, but it</span>
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<span class="comment">//can be returned from functions thanks to move semantics</span>
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<span class="identifier">file_descriptor</span> <span class="identifier">create_file_descriptor</span><span class="special">(</span><span class="keyword">const</span> <span class="keyword">char</span> <span class="special">*</span><span class="identifier">filename</span><span class="special">)</span>
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<span class="special">{</span> <span class="keyword">return</span> <span class="identifier">file_descriptor</span><span class="special">(</span><span class="identifier">filename</span><span class="special">);</span> <span class="special">}</span>
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<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
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<span class="special">{</span>
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<span class="comment">//Open a file obtaining its descriptor, the temporary</span>
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<span class="comment">//returned from 'create_file_descriptor' is moved to 'fd'.</span>
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<span class="identifier">file_descriptor</span> <span class="identifier">fd</span> <span class="special">=</span> <span class="identifier">create_file_descriptor</span><span class="special">(</span><span class="string">"filename"</span><span class="special">);</span>
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<span class="identifier">assert</span><span class="special">(!</span><span class="identifier">fd</span><span class="special">.</span><span class="identifier">empty</span><span class="special">());</span>
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<span class="comment">//Now move fd into a vector</span>
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<span class="identifier">boost</span><span class="special">::</span><span class="identifier">container</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="identifier">file_descriptor</span><span class="special">></span> <span class="identifier">v</span><span class="special">;</span>
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<span class="identifier">v</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">fd</span><span class="special">));</span>
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<span class="comment">//Check ownership has been transferred</span>
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<span class="identifier">assert</span><span class="special">(</span><span class="identifier">fd</span><span class="special">.</span><span class="identifier">empty</span><span class="special">());</span>
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<span class="identifier">assert</span><span class="special">(!</span><span class="identifier">v</span><span class="special">[</span><span class="number">0</span><span class="special">].</span><span class="identifier">empty</span><span class="special">());</span>
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<span class="comment">//Compilation error if uncommented since file_descriptor is not copyable</span>
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<span class="comment">//and vector copy construction requires value_type's copy constructor:</span>
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<span class="comment">//boost::container::vector<file_descriptor> v2(v);</span>
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<span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
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<span class="special">}</span>
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</pre>
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<p>
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<td align="right"><div class="copyright-footer">Copyright © 2008-2014 Ion Gaztanaga<p>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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