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| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_typetraits.examples.iter"></a><a class="link" href="iter.html" title="An improved Version of std::iter_swap">An improved Version of |
| std::iter_swap</a> |
| </h3></div></div></div> |
| <p> |
| Demonstrates a version of <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">iter_swap</span></code> |
| that use type traits to determine whether an it's arguments are proxy iterators |
| or not, if they're not then it just does a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">swap</span></code> |
| of it's dereferenced arguments (the same as <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">iter_swap</span></code> |
| does), however if they are proxy iterators then takes special care over the |
| swap to ensure that the algorithm works correctly for both proxy iterators, |
| and even iterators of different types (see <a href="../../../../examples/iter_swap_example.cpp" target="_top">iter_swap_example.cpp</a>): |
| </p> |
| <pre class="programlisting"><span class="comment">//</span> |
| <span class="comment">// iter_swap:</span> |
| <span class="comment">// tests whether iterator is a proxy iterator or not, and</span> |
| <span class="comment">// uses optimal form accordingly:</span> |
| <span class="comment">//</span> |
| <span class="keyword">namespace</span> <span class="identifier">detail</span><span class="special">{</span> |
| |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">I</span><span class="special">></span> |
| <span class="keyword">static</span> <span class="keyword">void</span> <span class="identifier">do_swap</span><span class="special">(</span><span class="identifier">I</span> <span class="identifier">one</span><span class="special">,</span> <span class="identifier">I</span> <span class="identifier">two</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><a class="link" href="../reference/integral_constant.html" title="integral_constant">false_type</a><span class="special">&)</span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">iterator_traits</span><span class="special"><</span><span class="identifier">I</span><span class="special">>::</span><span class="identifier">value_type</span> <span class="identifier">v_t</span><span class="special">;</span> |
| <span class="identifier">v_t</span> <span class="identifier">v</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">one</span><span class="special">;</span> |
| <span class="special">*</span><span class="identifier">one</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">two</span><span class="special">;</span> |
| <span class="special">*</span><span class="identifier">two</span> <span class="special">=</span> <span class="identifier">v</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">I</span><span class="special">></span> |
| <span class="keyword">static</span> <span class="keyword">void</span> <span class="identifier">do_swap</span><span class="special">(</span><span class="identifier">I</span> <span class="identifier">one</span><span class="special">,</span> <span class="identifier">I</span> <span class="identifier">two</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><a class="link" href="../reference/integral_constant.html" title="integral_constant">true_type</a><span class="special">&)</span> |
| <span class="special">{</span> |
| <span class="keyword">using</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">swap</span><span class="special">;</span> |
| <span class="identifier">swap</span><span class="special">(*</span><span class="identifier">one</span><span class="special">,</span> <span class="special">*</span><span class="identifier">two</span><span class="special">);</span> |
| <span class="special">}</span> |
| |
| <span class="special">}</span> |
| |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">I1</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">I2</span><span class="special">></span> |
| <span class="keyword">inline</span> <span class="keyword">void</span> <span class="identifier">iter_swap</span><span class="special">(</span><span class="identifier">I1</span> <span class="identifier">one</span><span class="special">,</span> <span class="identifier">I2</span> <span class="identifier">two</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="comment">//</span> |
| <span class="comment">// See is both arguments are non-proxying iterators, </span> |
| <span class="comment">// and if both iterator the same type:</span> |
| <span class="comment">//</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">iterator_traits</span><span class="special"><</span><span class="identifier">I1</span><span class="special">>::</span><span class="identifier">reference</span> <span class="identifier">r1_t</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">iterator_traits</span><span class="special"><</span><span class="identifier">I2</span><span class="special">>::</span><span class="identifier">reference</span> <span class="identifier">r2_t</span><span class="special">;</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><a class="link" href="../reference/integral_constant.html" title="integral_constant">integral_constant</a><span class="special"><</span><span class="keyword">bool</span><span class="special">,</span> |
| <span class="special">::</span><span class="identifier">boost</span><span class="special">::</span><a class="link" href="../reference/is_reference.html" title="is_reference">is_reference</a><span class="special"><</span><span class="identifier">r1_t</span><span class="special">>::</span><span class="identifier">value</span> |
| <span class="special">&&</span> <span class="special">::</span><span class="identifier">boost</span><span class="special">::</span><a class="link" href="../reference/is_reference.html" title="is_reference">is_reference</a><span class="special"><</span><span class="identifier">r2_t</span><span class="special">>::</span><span class="identifier">value</span> |
| <span class="special">&&</span> <span class="special">::</span><span class="identifier">boost</span><span class="special">::</span><a class="link" href="../reference/is_same.html" title="is_same">is_same</a><span class="special"><</span><span class="identifier">r1_t</span><span class="special">,</span> <span class="identifier">r2_t</span><span class="special">>::</span><span class="identifier">value</span><span class="special">></span> <span class="identifier">truth_type</span><span class="special">;</span> |
| |
| <span class="identifier">detail</span><span class="special">::</span><span class="identifier">do_swap</span><span class="special">(</span><span class="identifier">one</span><span class="special">,</span> <span class="identifier">two</span><span class="special">,</span> <span class="identifier">truth_type</span><span class="special">());</span> |
| <span class="special">}</span> |
| </pre> |
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