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20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="method_3_1.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../method_3.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../../../style_guide.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h5 class="title"> 27<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 28 3.2: Implement a Range Adaptor with arguments</a> 29</h5></div></div></div> 30<div class="orderedlist"><ol class="orderedlist" type="1"> 31<li class="listitem"> 32 Provide a range for your return type, for example: 33<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> 34<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> 35<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> 36 37<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Value</span><span class="special">></span> 38<span class="keyword">class</span> <span class="identifier">replace_value</span> 39<span class="special">{</span> 40<span class="keyword">public</span><span class="special">:</span> 41 <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> 42 <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> 43 44 <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> 45 <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> 46 <span class="special">{</span> 47 <span class="special">}</span> 48 49 <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> 50 <span class="special">{</span> 51 <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> 52 <span class="special">}</span> 53<span class="keyword">private</span><span class="special">:</span> 54 <span class="identifier">Value</span> <span class="identifier">m_from</span><span class="special">;</span> 55 <span class="identifier">Value</span> <span class="identifier">m_to</span><span class="special">;</span> 56<span class="special">};</span> 57 58<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Range</span><span class="special">></span> 59<span class="keyword">class</span> <span class="identifier">replace_range</span> 60<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> 61 <span class="identifier">boost</span><span class="special">::</span><span class="identifier">transform_iterator</span><span class="special"><</span> 62 <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> 63 <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> 64<span class="special">{</span> 65<span class="keyword">private</span><span class="special">:</span> 66 <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> 67 <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> 68 <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> 69 <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> 70 <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> 71 72<span class="keyword">public</span><span class="special">:</span> 73 <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> 74 <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> 75 <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> 76 <span class="special">{</span> 77 <span class="special">}</span> 78 <span class="special">};</span> 79</pre> 80 </li> 81<li class="listitem"> 82 Implement a holder class to hold the arguments required to construct 83 the RangeAdaptor. The holder combines multiple parameters into one 84 that can be passed as the right operand of <code class="computeroutput"><span class="keyword">operator</span><span class="special">|()</span></code>. 85<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> 86<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> 87<span class="special">{</span> 88<span class="keyword">public</span><span class="special">:</span> 89 <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> 90 <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> 91 <span class="special">{</span> <span class="special">}</span> 92<span class="keyword">private</span><span class="special">:</span> 93 <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> 94<span class="special">};</span> 95</pre> 96 </li> 97<li class="listitem"> 98 Define an instance of the holder with the name of the adaptor 99<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> 100<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> 101</pre> 102 </li> 103<li class="listitem"> 104 Define <code class="computeroutput"><span class="keyword">operator</span><span class="special">|</span></code> 105<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> 106<span class="keyword">inline</span> <span class="identifier">replace_range</span><span class="special"><</span><span class="identifier">SinglePassRange</span><span class="special">></span> 107<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> 108 <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> 109<span class="special">{</span> 110 <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> 111<span class="special">}</span> 112 113<span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">SinglePassRange</span><span class="special">></span> 114<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> 115<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> 116 <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> 117<span class="special">{</span> 118 <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> 119<span class="special">}</span> 120</pre> 121 </li> 122</ol></div> 123</div> 124<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 125<td align="left"></td> 126<td align="right"><div class="copyright-footer">Copyright © 2003-2010 Thorsten Ottosen, 127 Neil Groves<p> 128 Distributed under the Boost Software License, Version 1.0. (See accompanying 129 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>) 130 </p> 131</div></td> 132</tr></table> 133<hr> 134<div class="spirit-nav"> 135<a accesskey="p" href="method_3_1.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../method_3.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../../../style_guide.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 136</div> 137</body> 138</html> 139
