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| <a name="range.reference.extending.method_3.method_3_2"></a><a class="link" href="method_3_2.html" title="Method 3.2: Implement a Range Adaptor with arguments"> Method |
| 3.2: Implement a Range Adaptor with arguments</a> |
| </h5></div></div></div> |
| <div class="orderedlist"><ol class="orderedlist" type="1"> |
| <li class="listitem"> |
| Provide a range for your return type, for example: |
| <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">argument_fwd</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">iterator_range</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">iterator</span><span class="special">/</span><span class="identifier">transform_iterator</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Value</span><span class="special">></span> |
| <span class="keyword">class</span> <span class="identifier">replace_value</span> |
| <span class="special">{</span> |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="keyword">typedef</span> <span class="keyword">const</span> <span class="identifier">Value</span><span class="special">&</span> <span class="identifier">result_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="keyword">const</span> <span class="identifier">Value</span><span class="special">&</span> <span class="identifier">argument_type</span><span class="special">;</span> |
| |
| <span class="identifier">replace_value</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">Value</span><span class="special">&</span> <span class="identifier">from</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">Value</span><span class="special">&</span> <span class="identifier">to</span><span class="special">)</span> |
| <span class="special">:</span> <span class="identifier">m_from</span><span class="special">(</span><span class="identifier">from</span><span class="special">),</span> <span class="identifier">m_to</span><span class="special">(</span><span class="identifier">to</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">const</span> <span class="identifier">Value</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">()(</span><span class="keyword">const</span> <span class="identifier">Value</span><span class="special">&</span> <span class="identifier">x</span><span class="special">)</span> <span class="keyword">const</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="special">(</span><span class="identifier">x</span> <span class="special">==</span> <span class="identifier">m_from</span><span class="special">)</span> <span class="special">?</span> <span class="identifier">m_to</span> <span class="special">:</span> <span class="identifier">x</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="keyword">private</span><span class="special">:</span> |
| <span class="identifier">Value</span> <span class="identifier">m_from</span><span class="special">;</span> |
| <span class="identifier">Value</span> <span class="identifier">m_to</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">Range</span><span class="special">></span> |
| <span class="keyword">class</span> <span class="identifier">replace_range</span> |
| <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">iterator_range</span><span class="special"><</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">transform_iterator</span><span class="special"><</span> |
| <span class="identifier">replace_value</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_value</span><span class="special"><</span><span class="identifier">Range</span><span class="special">>::</span><span class="identifier">type</span><span class="special">>,</span> |
| <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_iterator</span><span class="special"><</span><span class="identifier">Range</span><span class="special">>::</span><span class="identifier">type</span><span class="special">></span> <span class="special">></span> |
| <span class="special">{</span> |
| <span class="keyword">private</span><span class="special">:</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_value</span><span class="special"><</span><span class="identifier">Range</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">value_type</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_iterator</span><span class="special"><</span><span class="identifier">Range</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">iterator_base</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">replace_value</span><span class="special"><</span><span class="identifier">value_type</span><span class="special">></span> <span class="identifier">Fn</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">transform_iterator</span><span class="special"><</span><span class="identifier">Fn</span><span class="special">,</span> <span class="identifier">iterator_base</span><span class="special">></span> <span class="identifier">replaced_iterator</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">iterator_range</span><span class="special"><</span><span class="identifier">replaced_iterator</span><span class="special">></span> <span class="identifier">base_t</span><span class="special">;</span> |
| |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="identifier">replace_range</span><span class="special">(</span><span class="identifier">Range</span><span class="special">&</span> <span class="identifier">rng</span><span class="special">,</span> <span class="identifier">value_type</span> <span class="identifier">from</span><span class="special">,</span> <span class="identifier">value_type</span> <span class="identifier">to</span><span class="special">)</span> |
| <span class="special">:</span> <span class="identifier">base_t</span><span class="special">(</span><span class="identifier">replaced_iterator</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">begin</span><span class="special">(</span><span class="identifier">rng</span><span class="special">),</span> <span class="identifier">Fn</span><span class="special">(</span><span class="identifier">from</span><span class="special">,</span><span class="identifier">to</span><span class="special">)),</span> |
| <span class="identifier">replaced_iterator</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">end</span><span class="special">(</span><span class="identifier">rng</span><span class="special">),</span> <span class="identifier">Fn</span><span class="special">(</span><span class="identifier">from</span><span class="special">,</span><span class="identifier">to</span><span class="special">)))</span> |
| <span class="special">{</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| </pre> |
| </li> |
| <li class="listitem"> |
| Implement a holder class to hold the arguments required to construct |
| the RangeAdaptor. |
| </li> |
| </ol></div> |
| <p> |
| The holder combines multiple parameters into one that can be passed as |
| the right operand of <code class="computeroutput"><span class="keyword">operator</span><span class="special">|()</span></code>. |
| </p> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">></span> |
| <span class="keyword">class</span> <span class="identifier">replace_holder</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_detail</span><span class="special">::</span><span class="identifier">holder2</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> |
| <span class="special">{</span> |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="identifier">replace_holder</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">from</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">to</span><span class="special">)</span> |
| <span class="special">:</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_detail</span><span class="special">::</span><span class="identifier">holder2</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">from</span><span class="special">,</span> <span class="identifier">to</span><span class="special">)</span> |
| <span class="special">{</span> <span class="special">}</span> |
| <span class="keyword">private</span><span class="special">:</span> |
| <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">=(</span><span class="keyword">const</span> <span class="identifier">replace_holder</span><span class="special">&);</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| </p> |
| <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"> |
| Define an instance of the holder with the name of the adaptor |
| </li></ol></div> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">static</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_detail</span><span class="special">::</span><span class="identifier">forwarder2</span><span class="special"><</span><span class="identifier">replace_holder</span><span class="special">></span> |
| <span class="identifier">replaced</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_detail</span><span class="special">::</span><span class="identifier">forwarder2</span><span class="special"><</span><span class="identifier">replace_holder</span><span class="special">>();</span> |
| </pre> |
| <p> |
| </p> |
| <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"> |
| Define <code class="computeroutput"><span class="keyword">operator</span><span class="special">|</span></code> |
| </li></ol></div> |
| <p> |
| |
| </p> |
| <pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">SinglePassRange</span><span class="special">></span> |
| <span class="keyword">inline</span> <span class="identifier">replace_range</span><span class="special"><</span><span class="identifier">SinglePassRange</span><span class="special">></span> |
| <span class="keyword">operator</span><span class="special">|(</span><span class="identifier">SinglePassRange</span><span class="special">&</span> <span class="identifier">rng</span><span class="special">,</span> |
| <span class="keyword">const</span> <span class="identifier">replace_holder</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_value</span><span class="special"><</span><span class="identifier">SinglePassRange</span><span class="special">>::</span><span class="identifier">type</span><span class="special">>&</span> <span class="identifier">f</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="identifier">replace_range</span><span class="special"><</span><span class="identifier">SinglePassRange</span><span class="special">>(</span><span class="identifier">rng</span><span class="special">,</span> <span class="identifier">f</span><span class="special">.</span><span class="identifier">val1</span><span class="special">,</span> <span class="identifier">f</span><span class="special">.</span><span class="identifier">val2</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">SinglePassRange</span><span class="special">></span> |
| <span class="keyword">inline</span> <span class="identifier">replace_range</span><span class="special"><</span><span class="keyword">const</span> <span class="identifier">SinglePassRange</span><span class="special">></span> |
| <span class="keyword">operator</span><span class="special">|(</span><span class="keyword">const</span> <span class="identifier">SinglePassRange</span><span class="special">&</span> <span class="identifier">rng</span><span class="special">,</span> |
| <span class="keyword">const</span> <span class="identifier">replace_holder</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_value</span><span class="special"><</span><span class="identifier">SinglePassRange</span><span class="special">>::</span><span class="identifier">type</span><span class="special">>&</span> <span class="identifier">f</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="identifier">replace_range</span><span class="special"><</span><span class="keyword">const</span> <span class="identifier">SinglePassRange</span><span class="special">>(</span><span class="identifier">rng</span><span class="special">,</span> <span class="identifier">f</span><span class="special">.</span><span class="identifier">val1</span><span class="special">,</span> <span class="identifier">f</span><span class="special">.</span><span class="identifier">val2</span><span class="special">);</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| </p> |
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| <td align="right"><div class="copyright-footer">Copyright © 2003 -2010 Thorsten Ottosen, Neil Groves<p> |
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| 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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