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  25 <div class="section">
  26 <div class="titlepage"><div><div><h5 class="title">
  27 <a name="geometry.reference.algorithms.for_each.for_each_segment"></a><a class="link" href="for_each_segment.html" title="for_each_segment">for_each_segment</a>
  28 </h5></div></div></div>
  29 <p>
  30             <a class="indexterm" name="idp117009648"></a>
  31 Applies function <span class="bold"><strong>f</strong></span> to each segment.
  32           </p>
  33 <h6>
  34 <a name="geometry.reference.algorithms.for_each.for_each_segment.h0"></a>
  35             <span class="phrase"><a name="geometry.reference.algorithms.for_each.for_each_segment.description"></a></span><a class="link" href="for_each_segment.html#geometry.reference.algorithms.for_each.for_each_segment.description">Description</a>
  36           </h6>
  37 <p>
  38             Applies a function <span class="bold"><strong>f</strong></span> (functor, having
  39             operator() defined) to each segment making up the geometry
  40           </p>
  41 <h6>
  42 <a name="geometry.reference.algorithms.for_each.for_each_segment.h1"></a>
  43             <span class="phrase"><a name="geometry.reference.algorithms.for_each.for_each_segment.synopsis"></a></span><a class="link" href="for_each_segment.html#geometry.reference.algorithms.for_each.for_each_segment.synopsis">Synopsis</a>
  44           </h6>
  45 <p>
  46 </p>
  47 <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Geometry</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Functor</span><span class="special">&gt;</span>
  48 <span class="identifier">Functor</span> <span class="identifier">for_each_segment</span><span class="special">(</span><span class="identifier">Geometry</span> <span class="special">&amp;</span> <span class="identifier">geometry</span><span class="special">,</span> <span class="identifier">Functor</span> <span class="identifier">f</span><span class="special">)</span></pre>
  49 <p>
  50           </p>
  51 <h6>
  52 <a name="geometry.reference.algorithms.for_each.for_each_segment.h2"></a>
  53             <span class="phrase"><a name="geometry.reference.algorithms.for_each.for_each_segment.parameters"></a></span><a class="link" href="for_each_segment.html#geometry.reference.algorithms.for_each.for_each_segment.parameters">Parameters</a>
  54           </h6>
  55 <div class="informaltable"><table class="table">
  56 <colgroup>
  57 <col>
  58 <col>
  59 <col>
  60 <col>
  61 </colgroup>
  62 <thead><tr>
  63 <th>
  64                     <p>
  65                       Type
  66                     </p>
  67                   </th>
  68 <th>
  69                     <p>
  70                       Concept
  71                     </p>
  72                   </th>
  73 <th>
  74                     <p>
  75                       Name
  76                     </p>
  77                   </th>
  78 <th>
  79                     <p>
  80                       Description
  81                     </p>
  82                   </th>
  83 </tr></thead>
  84 <tbody>
  85 <tr>
  86 <td>
  87                     <p>
  88                       Geometry &amp;
  89                     </p>
  90                   </td>
  91 <td>
  92                     <p>
  93                       Any type fulfilling a Geometry Concept
  94                     </p>
  95                   </td>
  96 <td>
  97                     <p>
  98                       geometry
  99                     </p>
 100                   </td>
 101 <td>
 102                     <p>
 103                       A model of the specified concept
 104                     </p>
 105                   </td>
 106 </tr>
 107 <tr>
 108 <td>
 109                     <p>
 110                       Functor
 111                     </p>
 112                   </td>
 113 <td>
 114                     <p>
 115                       Function or class with operator()
 116                     </p>
 117                   </td>
 118 <td>
 119                     <p>
 120                       f
 121                     </p>
 122                   </td>
 123 <td>
 124                     <p>
 125                       Unary function, taking a segment as argument
 126                     </p>
 127                   </td>
 128 </tr>
 129 </tbody>
 130 </table></div>
 131 <h6>
 132 <a name="geometry.reference.algorithms.for_each.for_each_segment.h3"></a>
 133             <span class="phrase"><a name="geometry.reference.algorithms.for_each.for_each_segment.header"></a></span><a class="link" href="for_each_segment.html#geometry.reference.algorithms.for_each.for_each_segment.header">Header</a>
 134           </h6>
 135 <p>
 136             Either
 137           </p>
 138 <p>
 139             <code class="computeroutput"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
 140           </p>
 141 <p>
 142             Or
 143           </p>
 144 <p>
 145             <code class="computeroutput"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">/</span><span class="identifier">algorithms</span><span class="special">/</span><span class="identifier">for_each</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
 146           </p>
 147 <h6>
 148 <a name="geometry.reference.algorithms.for_each.for_each_segment.h4"></a>
 149             <span class="phrase"><a name="geometry.reference.algorithms.for_each.for_each_segment.conformance"></a></span><a class="link" href="for_each_segment.html#geometry.reference.algorithms.for_each.for_each_segment.conformance">Conformance</a>
 150           </h6>
 151 <p>
 152             The function for_each_segment is not defined by OGC.
 153           </p>
 154 <p>
 155             The function for_each_segment conforms to the std::for_each function
 156             of the C++ std-library.
 157           </p>
 158 <h6>
 159 <a name="geometry.reference.algorithms.for_each.for_each_segment.h5"></a>
 160             <span class="phrase"><a name="geometry.reference.algorithms.for_each.for_each_segment.example"></a></span><a class="link" href="for_each_segment.html#geometry.reference.algorithms.for_each.for_each_segment.example">Example</a>
 161           </h6>
 162 <p>
 163             Sample using for_each_segment, using a functor to get the minimum and
 164             maximum length of a segment in a linestring
 165           </p>
 166 <p>
 167 </p>
 168 <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span>
 169
 170 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 171 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">/</span><span class="identifier">geometries</span><span class="special">/</span><span class="identifier">linestring</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 172 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">/</span><span class="identifier">geometries</span><span class="special">/</span><span class="identifier">point_xy</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 173
 174 <span class="preprocessor">#include</span> <span class="special">&lt;</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">&gt;</span>
 175
 176
 177 <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Segment</span><span class="special">&gt;</span>
 178 <span class="keyword">struct</span> <span class="identifier">gather_segment_statistics</span>
 179 <span class="special">{</span>
 180     <span class="comment">// Remember that if coordinates are integer, the length might be floating point</span>
 181     <span class="comment">// So use "double" for integers. In other cases, use coordinate type</span>
 182     <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">select_most_precise</span>
 183         <span class="special">&lt;</span>
 184             <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">coordinate_type</span><span class="special">&lt;</span><span class="identifier">Segment</span><span class="special">&gt;::</span><span class="identifier">type</span><span class="special">,</span>
 185             <span class="keyword">double</span>
 186         <span class="special">&gt;::</span><span class="identifier">type</span> <span class="identifier">type</span><span class="special">;</span>
 187
 188     <span class="identifier">type</span> <span class="identifier">min_length</span><span class="special">,</span> <span class="identifier">max_length</span><span class="special">;</span>
 189
 190     <span class="comment">// Initialize min and max</span>
 191     <span class="identifier">gather_segment_statistics</span><span class="special">()</span>
 192         <span class="special">:</span> <span class="identifier">min_length</span><span class="special">(</span><span class="number">1e38</span><span class="special">)</span>
 193         <span class="special">,</span> <span class="identifier">max_length</span><span class="special">(-</span><span class="number">1</span><span class="special">)</span>
 194     <span class="special">{}</span>
 195
 196     <span class="comment">// This operator is called for each segment</span>
 197     <span class="keyword">inline</span> <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()(</span><span class="identifier">Segment</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">s</span><span class="special">)</span>
 198     <span class="special">{</span>
 199         <span class="identifier">type</span> <span class="identifier">length</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">length</span><span class="special">(</span><span class="identifier">s</span><span class="special">);</span>
 200         <span class="keyword">if</span> <span class="special">(</span><span class="identifier">length</span> <span class="special">&lt;</span> <span class="identifier">min_length</span><span class="special">)</span> <span class="identifier">min_length</span> <span class="special">=</span> <span class="identifier">length</span><span class="special">;</span>
 201         <span class="keyword">if</span> <span class="special">(</span><span class="identifier">length</span> <span class="special">&gt;</span> <span class="identifier">max_length</span><span class="special">)</span> <span class="identifier">max_length</span> <span class="special">=</span> <span class="identifier">length</span><span class="special">;</span>
 202     <span class="special">}</span>
 203 <span class="special">};</span>
 204
 205 <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
 206 <span class="special">{</span>
 207     <span class="comment">// Bring "+=" for a vector into scope</span>
 208     <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>
 209
 210     <span class="comment">// Define a type</span>
 211     <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">model</span><span class="special">::</span><span class="identifier">d2</span><span class="special">::</span><span class="identifier">point_xy</span><span class="special">&lt;</span><span class="keyword">double</span><span class="special">&gt;</span> <span class="identifier">point</span><span class="special">;</span>
 212
 213     <span class="comment">// Declare a linestring</span>
 214     <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">model</span><span class="special">::</span><span class="identifier">linestring</span><span class="special">&lt;</span><span class="identifier">point</span><span class="special">&gt;</span> <span class="identifier">polyline</span><span class="special">;</span>
 215
 216     <span class="comment">// Use Boost.Assign to initialize a linestring</span>
 217     <span class="identifier">polyline</span> <span class="special">+=</span> <span class="identifier">point</span><span class="special">(</span><span class="number">0</span><span class="special">,</span> <span class="number">0</span><span class="special">),</span> <span class="identifier">point</span><span class="special">(</span><span class="number">3</span><span class="special">,</span> <span class="number">3</span><span class="special">),</span> <span class="identifier">point</span><span class="special">(</span><span class="number">5</span><span class="special">,</span> <span class="number">1</span><span class="special">),</span> <span class="identifier">point</span><span class="special">(</span><span class="number">6</span><span class="special">,</span> <span class="number">2</span><span class="special">),</span>
 218                 <span class="identifier">point</span><span class="special">(</span><span class="number">8</span><span class="special">,</span> <span class="number">0</span><span class="special">),</span> <span class="identifier">point</span><span class="special">(</span><span class="number">4</span><span class="special">,</span> <span class="special">-</span><span class="number">4</span><span class="special">),</span> <span class="identifier">point</span><span class="special">(</span><span class="number">1</span><span class="special">,</span> <span class="special">-</span><span class="number">1</span><span class="special">),</span> <span class="identifier">point</span><span class="special">(</span><span class="number">3</span><span class="special">,</span> <span class="number">2</span><span class="special">);</span>
 219
 220
 221     <span class="comment">// Declare the gathering class...</span>
 222     <span class="identifier">gather_segment_statistics</span>
 223         <span class="special">&lt;</span>
 224             <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">model</span><span class="special">::</span><span class="identifier">referring_segment</span><span class="special">&lt;</span><span class="identifier">point</span><span class="special">&gt;</span>
 225         <span class="special">&gt;</span> <span class="identifier">functor</span><span class="special">;</span>
 226
 227     <span class="comment">// ... and use it, the essention.</span>
 228     <span class="comment">// As also in std::for_each it is a const value, so retrieve it as a return value.</span>
 229     <span class="identifier">functor</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">for_each_segment</span><span class="special">(</span><span class="identifier">polyline</span><span class="special">,</span> <span class="identifier">functor</span><span class="special">);</span>
 230
 231     <span class="comment">// Output the results</span>
 232     <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span>
 233         <span class="special">&lt;&lt;</span> <span class="string">"Min segment length: "</span> <span class="special">&lt;&lt;</span> <span class="identifier">functor</span><span class="special">.</span><span class="identifier">min_length</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span>
 234         <span class="special">&lt;&lt;</span> <span class="string">"Max segment length: "</span> <span class="special">&lt;&lt;</span> <span class="identifier">functor</span><span class="special">.</span><span class="identifier">max_length</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
 235
 236     <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
 237 <span class="special">}</span>
 238 </pre>
 239 <p>
 240           </p>
 241 <p>
 242             Output:
 243           </p>
 244 <pre class="programlisting">Min segment length: 1.41421
 245 Max segment length: 5.65685
 246 </pre>
 247 </div>
 248 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 249 <td align="left"></td>
 250 <td align="right"><div class="copyright-footer">Copyright &#169; 2009-2014 Barend Gehrels, Bruno Lalande, Mateusz Loskot, Adam
 251       Wulkiewicz, Oracle and/or its affiliates<p>
 252         Distributed under the Boost Software License, Version 1.0. (See accompanying
 253         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>)
 254       </p>
 255 </div></td>
 256 </tr></table>
 257 <hr>
 258 <div class="spirit-nav">
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