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| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="range.reference.adaptors.reference.type_erased"></a><a class="link" href="type_erased.html" title="type_erased">type_erased</a> |
| </h5></div></div></div> |
| <div class="toc"><dl><dt><span class="section"><a href="type_erased.html#range.reference.adaptors.reference.type_erased.type_erased_example">type-erased |
| example</a></span></dt></dl></div> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| Syntax |
| </p> |
| </th> |
| <th> |
| <p> |
| Code |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| Pipe |
| </p> |
| </td> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="identifier">rng</span> <span class="special">|</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">adaptors</span><span class="special">::</span><span class="identifier">type_erased</span><span class="special"><</span><span class="identifier">Value</span><span class="special">,</span> |
| <span class="identifier">Traversal</span><span class="special">,</span> |
| <span class="identifier">Reference</span><span class="special">,</span> |
| <span class="identifier">Difference</span><span class="special">,</span> |
| <span class="identifier">Buffer</span><span class="special">>()</span></code> |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| Function |
| </p> |
| </td> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">adaptors</span><span class="special">::</span><span class="identifier">type_erase</span><span class="special">(</span><span class="identifier">rng</span><span class="special">,</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">adaptors</span><span class="special">::</span><span class="identifier">type_erased</span><span class="special"><</span><span class="identifier">Value</span><span class="special">,</span> |
| <span class="identifier">Traversal</span><span class="special">,</span> |
| <span class="identifier">Reference</span><span class="special">,</span> |
| <span class="identifier">Difference</span><span class="special">,</span> |
| <span class="identifier">Buffer</span><span class="special">>)</span></code> |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| <p> |
| Please note that it is frequently unnecessary to use the <code class="computeroutput"><span class="identifier">type_erased</span></code> adaptor. It is often better |
| to use the implicit conversion to <code class="computeroutput"><span class="identifier">any_range</span></code>. |
| </p> |
| <p> |
| Let <code class="computeroutput"><span class="identifier">Rng</span></code> be the type of |
| <code class="computeroutput"><span class="identifier">rng</span></code>. |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| <p class="simpara"> |
| <span class="bold"><strong>Template parameters:</strong></span> |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="circle"> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">Value</span></code> is the |
| <code class="computeroutput"><span class="identifier">value_type</span></code> for |
| the <code class="computeroutput"><span class="identifier">any_range</span></code>. |
| If this is set to boost::use_default, <code class="computeroutput"><span class="identifier">Value</span></code> |
| will be calculated from the range type when the adaptor is applied. |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">Traversal</span></code> is |
| the tag used to identify the traversal of the resultant range. |
| Frequently it is desireable to set a traversal category lower |
| than the source container or range to maximize the number of |
| ranges that can convert to the <code class="computeroutput"><span class="identifier">any_range</span></code>. |
| If this is left as boost::use_default then <code class="computeroutput"><span class="identifier">Traversal</span></code> |
| will be <code class="computeroutput"><span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">iterator_traversal</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_iterator</span><span class="special"><</span><span class="identifier">Rng</span><span class="special">>::</span><span class="identifier">type</span><span class="special">>::</span><span class="identifier">type</span></code> |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">Reference</span></code> is |
| the <code class="computeroutput"><span class="identifier">reference</span></code> |
| for the <code class="computeroutput"><span class="identifier">any_range</span></code>. |
| <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">use_default</span></code> will equate to |
| <code class="computeroutput"><span class="keyword">typename</span> <span class="identifier">range_reference</span><span class="special"><</span><span class="identifier">Rng</span><span class="special">>::</span><span class="identifier">type</span></code>. |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">Difference</span></code> is |
| the <code class="computeroutput"><span class="identifier">difference_type</span></code> |
| for the any_range. <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">use_default</span></code> |
| will equate to <code class="computeroutput"><span class="keyword">typename</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_difference</span><span class="special"><</span><span class="identifier">Rng</span><span class="special">>::</span><span class="identifier">type</span></code> |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">Buffer</span></code> is the |
| storage used to allocate the underlying iterator wrappers. This |
| can typically be ignored, but is available as a template parameter |
| for customization. Buffer must be a model of the <code class="computeroutput"><span class="identifier">AnyIteratorBufferConcept</span></code>. |
| </li> |
| </ul></div> |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Precondition:</strong></span> <code class="computeroutput"><span class="identifier">Traversal</span></code> |
| is one of <code class="computeroutput"><span class="special">{</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">use_default</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">single_pass_traversal_tag</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">forward_traversal_tag</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">bidirectional_traversal_tag</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">random_access_traversal_tag</span> |
| <span class="special">}</span></code> |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Returns:</strong></span> The returned value is the |
| same as <code class="computeroutput"><span class="keyword">typename</span> <span class="identifier">any_range_type_generator</span><span class="special"><</span> <span class="identifier">Rng</span><span class="special">,</span> <span class="identifier">Value</span><span class="special">,</span> <span class="identifier">Traversal</span><span class="special">,</span> <span class="identifier">Reference</span><span class="special">,</span> <span class="identifier">Difference</span><span class="special">,</span> <span class="identifier">Buffer</span> |
| <span class="special">></span></code> that represents <code class="computeroutput"><span class="identifier">rng</span></code> in a type-erased manner. |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Range Category:</strong></span> <a class="link" href="../../../concepts/single_pass_range.html" title="Single Pass Range">Single |
| Pass Range</a> |
| </li> |
| <li class="listitem"> |
| <span class="bold"><strong>Returned Range Category:</strong></span> if <code class="computeroutput"><span class="identifier">Traversal</span></code> was specified as <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">use_default</span></code> then <code class="computeroutput"><span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">iterator_traversal</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_iterator</span><span class="special"><</span><span class="identifier">Rng</span><span class="special">>::</span><span class="identifier">type</span><span class="special">>::</span><span class="identifier">type</span></code>, |
| otherwise <code class="computeroutput"><span class="identifier">Traversal</span></code>. |
| </li> |
| </ul></div> |
| <a name="range.reference.adaptors.reference.type_erased.anyiteratorbufferconcept"></a><h6> |
| <a name="id677095"></a> |
| <a class="link" href="type_erased.html#range.reference.adaptors.reference.type_erased.anyiteratorbufferconcept">AnyIteratorBufferConcept</a> |
| </h6> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">AnyIteratorBufferConcept</span> |
| <span class="special">{</span> |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="identifier">AnyIteratorBufferConcept</span><span class="special">();</span> |
| <span class="special">~</span><span class="identifier">AnyIteratorBufferConcept</span><span class="special">();</span> |
| |
| <span class="comment">// bytes is the requested size to allocate. This function |
| </span> <span class="comment">// must return a pointer to an adequate area of memory. |
| </span> <span class="comment">// throws: bad_alloc |
| </span> <span class="comment">// |
| </span> <span class="comment">// The buffer will only ever have zero or one |
| </span> <span class="comment">// outstanding memory allocations. |
| </span> <span class="keyword">void</span><span class="special">*</span> <span class="identifier">allocate</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">bytes</span><span class="special">);</span> |
| |
| <span class="comment">// deallocate this buffer |
| </span> <span class="keyword">void</span> <span class="identifier">deallocate</span><span class="special">();</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| </p> |
| <div class="section"> |
| <div class="titlepage"><div><div><h6 class="title"> |
| <a name="range.reference.adaptors.reference.type_erased.type_erased_example"></a><a class="link" href="type_erased.html#range.reference.adaptors.reference.type_erased.type_erased_example" title="type-erased example">type-erased |
| example</a> |
| </h6></div></div></div> |
| <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">range</span><span class="special">/</span><span class="identifier">adaptor</span><span class="special">/</span><span class="identifier">type_erased</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">range</span><span class="special">/</span><span class="identifier">algorithm</span><span class="special">/</span><span class="identifier">copy</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">assign</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">foreach</span><span class="special">.</span><span class="identifier">hpp</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="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">list</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">vector</span><span class="special">></span> |
| |
| <span class="comment">// The client interface from an OO perspective merely requires a sequence |
| </span><span class="comment">// of integers that can be forward traversed |
| </span><span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">any_range</span><span class="special"><</span> |
| <span class="keyword">int</span> |
| <span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">forward_traversal_tag</span> |
| <span class="special">,</span> <span class="keyword">int</span> |
| <span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">ptrdiff_t</span> |
| <span class="special">></span> <span class="identifier">integer_range</span><span class="special">;</span> |
| |
| <span class="keyword">namespace</span> <span class="identifier">server</span> |
| <span class="special">{</span> |
| <span class="keyword">void</span> <span class="identifier">display_integers</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">integer_range</span><span class="special">&</span> <span class="identifier">rng</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">copy</span><span class="special">(</span><span class="identifier">rng</span><span class="special">,</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream_iterator</span><span class="special"><</span><span class="keyword">int</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="string">","</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">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">namespace</span> <span class="identifier">client</span> |
| <span class="special">{</span> |
| <span class="keyword">void</span> <span class="identifier">run</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">assign</span><span class="special">;</span> |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">adaptors</span><span class="special">;</span> |
| |
| <span class="comment">// Under most conditions one would simply use an appropriate |
| </span> <span class="comment">// any_range as a function parameter. The type_erased adaptor |
| </span> <span class="comment">// is often superfluous. However because the type_erased |
| </span> <span class="comment">// adaptor is applied to a range, we can use default template |
| </span> <span class="comment">// arguments that are generated in conjunction with the |
| </span> <span class="comment">// range type to which we are applying the adaptor. |
| </span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">input</span><span class="special">;</span> |
| <span class="identifier">input</span> <span class="special">+=</span> <span class="number">1</span><span class="special">,</span><span class="number">2</span><span class="special">,</span><span class="number">3</span><span class="special">,</span><span class="number">4</span><span class="special">,</span><span class="number">5</span><span class="special">;</span> |
| |
| <span class="comment">// Note that this call is to a non-template function |
| </span> <span class="identifier">server</span><span class="special">::</span><span class="identifier">display_integers</span><span class="special">(</span><span class="identifier">input</span><span class="special">);</span> |
| |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">list</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">input2</span><span class="special">;</span> |
| <span class="identifier">input2</span> <span class="special">+=</span> <span class="number">6</span><span class="special">,</span><span class="number">7</span><span class="special">,</span><span class="number">8</span><span class="special">,</span><span class="number">9</span><span class="special">,</span><span class="number">10</span><span class="special">;</span> |
| |
| <span class="comment">// Note that this call is to the same non-tempate function |
| </span> <span class="identifier">server</span><span class="special">::</span><span class="identifier">display_integers</span><span class="special">(</span><span class="identifier">input2</span><span class="special">);</span> |
| |
| <span class="identifier">input2</span><span class="special">.</span><span class="identifier">clear</span><span class="special">();</span> |
| <span class="identifier">input2</span> <span class="special">+=</span> <span class="number">11</span><span class="special">,</span><span class="number">12</span><span class="special">,</span><span class="number">13</span><span class="special">,</span><span class="number">14</span><span class="special">,</span><span class="number">15</span><span class="special">;</span> |
| |
| <span class="comment">// Calling using the adaptor looks like this: |
| </span> <span class="comment">// Notice that here I have a type_erased that would be a |
| </span> <span class="comment">// bidirectional_traversal_tag, but this is convertible |
| </span> <span class="comment">// to the forward_traversal_tag equivalent hence this |
| </span> <span class="comment">// works. |
| </span> <span class="identifier">server</span><span class="special">::</span><span class="identifier">display_integers</span><span class="special">(</span><span class="identifier">input2</span> <span class="special">|</span> <span class="identifier">type_erased</span><span class="special"><>());</span> |
| |
| <span class="comment">// However we may simply wish to define an adaptor that |
| </span> <span class="comment">// takes a range and makes it into an appropriate |
| </span> <span class="comment">// forward_traversal any_range... |
| </span> <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">adaptors</span><span class="special">::</span><span class="identifier">type_erased</span><span class="special"><</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">use_default</span> |
| <span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">forward_traversal_tag</span> |
| <span class="special">></span> <span class="identifier">type_erased_forward</span><span class="special">;</span> |
| |
| <span class="comment">// This adaptor can turn other containers with different |
| </span> <span class="comment">// value_types and reference_types into the appropriate |
| </span> <span class="comment">// any_range. |
| </span> |
| <span class="identifier">server</span><span class="special">::</span><span class="identifier">display_integers</span><span class="special">(</span><span class="identifier">input2</span> <span class="special">|</span> <span class="identifier">type_erased_forward</span><span class="special">());</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="keyword">int</span> <span class="identifier">argc</span><span class="special">,</span> <span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">argv</span><span class="special">[])</span> |
| <span class="special">{</span> |
| <span class="identifier">client</span><span class="special">::</span><span class="identifier">run</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> |
| </div> |
| <p> |
| This would produce the output: |
| </p> |
| <pre class="programlisting"><span class="number">1</span><span class="special">,</span><span class="number">2</span><span class="special">,</span><span class="number">3</span><span class="special">,</span><span class="number">4</span><span class="special">,</span><span class="number">5</span> |
| <span class="number">6</span><span class="special">,</span><span class="number">7</span><span class="special">,</span><span class="number">8</span><span class="special">,</span><span class="number">9</span><span class="special">,</span><span class="number">10</span> |
| <span class="number">11</span><span class="special">,</span><span class="number">12</span><span class="special">,</span><span class="number">13</span><span class="special">,</span><span class="number">14</span><span class="special">,</span><span class="number">15</span> |
| <span class="number">11</span><span class="special">,</span><span class="number">12</span><span class="special">,</span><span class="number">13</span><span class="special">,</span><span class="number">14</span><span class="special">,</span><span class="number">15</span> |
| </pre> |
| <p> |
| </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 © 2003 -2010 Thorsten Ottosen, Neil Groves<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
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