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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 a 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="preprocessor">#include</span> <span class="special"><</span><span class="identifier">algorithm</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 insert into l2 containers</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">copy</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">l</span><span class="special">.</span><span class="identifier">end</span><span class="special">(),</span> <span class="identifier">mit</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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| <td align="right"><div class="copyright-footer">Copyright © 2008-2014 Ion Gaztanaga<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>) |
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