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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="move.move_inserters"></a><a class="link" href="move_inserters.html" title="Move inserters">Move inserters</a>
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<p>
Similar to standard insert iterators, it's possible to deal with move insertion
in the same way as writing into an array. A special kind of iterator adaptors,
called move insert iterators, are provided with this library. With regular
iterator classes,
</p>
<pre class="programlisting"><span class="keyword">while</span> <span class="special">(</span><span class="identifier">first</span> <span class="special">!=</span> <span class="identifier">last</span><span class="special">)</span> <span class="special">*</span><span class="identifier">result</span><span class="special">++</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">first</span><span class="special">++;</span>
</pre>
<p>
causes a range [first,last) to be copied into a range starting with result.
The same code with result being an move insert iterator will move insert corresponding
elements into the container. This device allows all of the copying algorithms
in the library to work in the move insert mode instead of the regular overwrite
mode. This library offers 3 move insert iterators and their helper functions:
</p>
<pre class="programlisting"><span class="comment">// Note: C models Container</span>
<span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">C</span><span class="special">></span>
<span class="keyword">class</span> <span class="identifier">back_move_insert_iterator</span><span class="special">;</span>
<span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">C</span><span class="special">></span>
<span class="identifier">back_move_insert_iterator</span><span class="special"><</span><span class="identifier">C</span><span class="special">></span> <span class="identifier">back_move_inserter</span><span class="special">(</span><span class="identifier">C</span><span class="special">&</span> <span class="identifier">x</span><span class="special">);</span>
<span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">C</span><span class="special">></span>
<span class="keyword">class</span> <span class="identifier">front_move_insert_iterator</span><span class="special">;</span>
<span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">C</span><span class="special">></span>
<span class="identifier">front_move_insert_iterator</span><span class="special"><</span><span class="identifier">C</span><span class="special">></span> <span class="identifier">front_move_inserter</span><span class="special">(</span><span class="identifier">C</span><span class="special">&</span> <span class="identifier">x</span><span class="special">);</span>
<span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">C</span><span class="special">></span>
<span class="keyword">class</span> <span class="identifier">move_insert_iterator</span><span class="special">;</span>
<span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">C</span><span class="special">></span>
<span class="identifier">move_insert_iterator</span><span class="special"><</span><span class="identifier">C</span><span class="special">></span> <span class="identifier">move_inserter</span><span class="special">(</span><span class="identifier">C</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">C</span><span class="special">::</span><span class="identifier">iterator</span> <span class="identifier">it</span><span class="special">);</span>
</pre>
<p>
A move insert iterator is constructed from a container and possibly one of
its iterators pointing to where insertion takes place if it is neither at the
beginning nor at the end of the container. Insert iterators satisfy the requirements
of output iterators. <code class="computeroutput"><span class="keyword">operator</span><span class="special">*</span></code> returns the move insert iterator itself. The
assignment <code class="computeroutput"><span class="keyword">operator</span><span class="special">=(</span><span class="identifier">T</span><span class="special">&</span> <span class="identifier">x</span><span class="special">)</span></code> is defined on insert iterators to allow writing
into them, it inserts x right before where the insert iterator is pointing.
In other words, an <code class="computeroutput"><span class="identifier">insert</span> <span class="identifier">iterator</span></code> is like a cursor pointing into the
container where the insertion takes place. <code class="computeroutput"><span class="identifier">back_move_iterator</span></code>
move inserts elements at the end of a container, <code class="computeroutput"><span class="identifier">front_insert_iterator</span></code>
move inserts elements at the beginning of a container, and <code class="computeroutput"><span class="identifier">move_insert_iterator</span></code>
move inserts elements where the iterator points to in a container. <code class="computeroutput"><span class="identifier">back_move_inserter</span></code>, <code class="computeroutput"><span class="identifier">front_move_inserter</span></code>,
and <code class="computeroutput"><span class="identifier">move_inserter</span></code> are three
functions making the insert iterators out of a container. Here's an example
of how to use them:
</p>
<p>
</p>
<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">list</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
<span class="preprocessor">#include</span> <span class="string">"movable.hpp"</span>
<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">cassert</span><span class="special">></span>
<span class="keyword">using</span> <span class="keyword">namespace</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="keyword">typedef</span> <span class="identifier">list</span><span class="special"><</span><span class="identifier">movable</span><span class="special">></span> <span class="identifier">list_t</span><span class="special">;</span>
<span class="keyword">typedef</span> <span class="identifier">list_t</span><span class="special">::</span><span class="identifier">iterator</span> <span class="identifier">l_iterator</span><span class="special">;</span>
<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">MoveInsertIterator</span><span class="special">></span>
<span class="keyword">void</span> <span class="identifier">test_move_inserter</span><span class="special">(</span><span class="identifier">list_t</span> <span class="special">&</span><span class="identifier">l2</span><span class="special">,</span> <span class="identifier">MoveInsertIterator</span> <span class="identifier">mit</span><span class="special">)</span>
<span class="special">{</span>
<span class="comment">//Create a list with 10 default constructed objects</span>
<span class="identifier">list</span><span class="special"><</span><span class="identifier">movable</span><span class="special">></span> <span class="identifier">l</span><span class="special">(</span><span class="number">10</span><span class="special">);</span>
<span class="identifier">assert</span><span class="special">(!</span><span class="identifier">l</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()-></span><span class="identifier">moved</span><span class="special">());</span>
<span class="identifier">l2</span><span class="special">.</span><span class="identifier">clear</span><span class="special">();</span>
<span class="comment">//Move construct</span>
<span class="keyword">for</span><span class="special">(</span><span class="identifier">l_iterator</span> <span class="identifier">itbeg</span> <span class="special">=</span> <span class="identifier">l</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">itend</span> <span class="special">=</span> <span class="identifier">l</span><span class="special">.</span><span class="identifier">end</span><span class="special">();</span> <span class="identifier">itbeg</span> <span class="special">!=</span> <span class="identifier">itend</span><span class="special">;</span> <span class="special">++</span><span class="identifier">itbeg</span><span class="special">){</span>
<span class="special">*</span><span class="identifier">mit</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">itbeg</span><span class="special">;</span>
<span class="special">}</span>
<span class="comment">//Check size and status</span>
<span class="identifier">assert</span><span class="special">(</span><span class="identifier">l2</span><span class="special">.</span><span class="identifier">size</span><span class="special">()</span> <span class="special">==</span> <span class="identifier">l</span><span class="special">.</span><span class="identifier">size</span><span class="special">());</span>
<span class="identifier">assert</span><span class="special">(</span><span class="identifier">l</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()-></span><span class="identifier">moved</span><span class="special">());</span>
<span class="identifier">assert</span><span class="special">(!</span><span class="identifier">l2</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()-></span><span class="identifier">moved</span><span class="special">());</span>
<span class="special">}</span>
<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
<span class="special">{</span>
<span class="identifier">list_t</span> <span class="identifier">l2</span><span class="special">;</span>
<span class="identifier">test_move_inserter</span><span class="special">(</span><span class="identifier">l2</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">back_move_inserter</span><span class="special">(</span><span class="identifier">l2</span><span class="special">));</span>
<span class="identifier">test_move_inserter</span><span class="special">(</span><span class="identifier">l2</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">front_move_inserter</span><span class="special">(</span><span class="identifier">l2</span><span class="special">));</span>
<span class="identifier">test_move_inserter</span><span class="special">(</span><span class="identifier">l2</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">move_inserter</span><span class="special">(</span><span class="identifier">l2</span><span class="special">,</span> <span class="identifier">l2</span><span class="special">.</span><span class="identifier">end</span><span class="special">()));</span>
<span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
</p>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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