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  26 <div class="titlepage"><div><div><h5 class="title">
  27 <a name="geometry.reference.algorithms.length.length_2_with_strategy"></a><a class="link" href="length_2_with_strategy.html" title="length (with strategy)">length
  28           (with strategy)</a>
  29 </h5></div></div></div>
  30 <p>
  31             <a class="indexterm" name="idp101137568"></a>
  32 Calculates the length of a geometry using the specified strategy.
  33           </p>
  34 <h6>
  35 <a name="geometry.reference.algorithms.length.length_2_with_strategy.h0"></a>
  36             <span class="phrase"><a name="geometry.reference.algorithms.length.length_2_with_strategy.description"></a></span><a class="link" href="length_2_with_strategy.html#geometry.reference.algorithms.length.length_2_with_strategy.description">Description</a>
  37           </h6>
  38 <p>
  39             The free function length calculates the length (the sum of distances
  40             between consecutive points) of a geometry using the specified strategy.
  41             Reasons to specify a strategy include: use another coordinate system
  42             for calculations; construct the strategy beforehand (e.g. with the radius
  43             of the Earth); select a strategy when there are more than one available
  44             for a calculation.
  45           </p>
  46 <h6>
  47 <a name="geometry.reference.algorithms.length.length_2_with_strategy.h1"></a>
  48             <span class="phrase"><a name="geometry.reference.algorithms.length.length_2_with_strategy.synopsis"></a></span><a class="link" href="length_2_with_strategy.html#geometry.reference.algorithms.length.length_2_with_strategy.synopsis">Synopsis</a>
  49           </h6>
  50 <p>
  51 </p>
  52 <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">Strategy</span><span class="special">&gt;</span>
  53 <span class="identifier">default_length_result</span><span class="special">&lt;</span><span class="identifier">Geometry</span><span class="special">&gt;::</span><span class="identifier">type</span> <span class="identifier">length</span><span class="special">(</span><span class="identifier">Geometry</span> <span class="keyword">const</span> <span class="special">&amp;</span> <span class="identifier">geometry</span><span class="special">,</span> <span class="identifier">Strategy</span> <span class="keyword">const</span> <span class="special">&amp;</span> <span class="identifier">strategy</span><span class="special">)</span></pre>
  54 <p>
  55           </p>
  56 <h6>
  57 <a name="geometry.reference.algorithms.length.length_2_with_strategy.h2"></a>
  58             <span class="phrase"><a name="geometry.reference.algorithms.length.length_2_with_strategy.parameters"></a></span><a class="link" href="length_2_with_strategy.html#geometry.reference.algorithms.length.length_2_with_strategy.parameters">Parameters</a>
  59           </h6>
  60 <div class="informaltable"><table class="table">
  61 <colgroup>
  62 <col>
  63 <col>
  64 <col>
  65 <col>
  66 </colgroup>
  67 <thead><tr>
  68 <th>
  69                     <p>
  70                       Type
  71                     </p>
  72                   </th>
  73 <th>
  74                     <p>
  75                       Concept
  76                     </p>
  77                   </th>
  78 <th>
  79                     <p>
  80                       Name
  81                     </p>
  82                   </th>
  83 <th>
  84                     <p>
  85                       Description
  86                     </p>
  87                   </th>
  88 </tr></thead>
  89 <tbody>
  90 <tr>
  91 <td>
  92                     <p>
  93                       Geometry const &amp;
  94                     </p>
  95                   </td>
  96 <td>
  97                     <p>
  98                       Any type fulfilling a Geometry Concept
  99                     </p>
 100                   </td>
 101 <td>
 102                     <p>
 103                       geometry
 104                     </p>
 105                   </td>
 106 <td>
 107                     <p>
 108                       A model of the specified concept
 109                     </p>
 110                   </td>
 111 </tr>
 112 <tr>
 113 <td>
 114                     <p>
 115                       Strategy const &amp;
 116                     </p>
 117                   </td>
 118 <td>
 119                     <p>
 120                       Any type fulfilling a distance Strategy Concept
 121                     </p>
 122                   </td>
 123 <td>
 124                     <p>
 125                       strategy
 126                     </p>
 127                   </td>
 128 <td>
 129                     <p>
 130                       The strategy which will be used for distance calculations
 131                     </p>
 132                   </td>
 133 </tr>
 134 </tbody>
 135 </table></div>
 136 <h6>
 137 <a name="geometry.reference.algorithms.length.length_2_with_strategy.h3"></a>
 138             <span class="phrase"><a name="geometry.reference.algorithms.length.length_2_with_strategy.returns"></a></span><a class="link" href="length_2_with_strategy.html#geometry.reference.algorithms.length.length_2_with_strategy.returns">Returns</a>
 139           </h6>
 140 <p>
 141             The calculated length
 142           </p>
 143 <h6>
 144 <a name="geometry.reference.algorithms.length.length_2_with_strategy.h4"></a>
 145             <span class="phrase"><a name="geometry.reference.algorithms.length.length_2_with_strategy.header"></a></span><a class="link" href="length_2_with_strategy.html#geometry.reference.algorithms.length.length_2_with_strategy.header">Header</a>
 146           </h6>
 147 <p>
 148             Either
 149           </p>
 150 <p>
 151             <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>
 152           </p>
 153 <p>
 154             Or
 155           </p>
 156 <p>
 157             <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">length</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
 158           </p>
 159 <h6>
 160 <a name="geometry.reference.algorithms.length.length_2_with_strategy.h5"></a>
 161             <span class="phrase"><a name="geometry.reference.algorithms.length.length_2_with_strategy.conformance"></a></span><a class="link" href="length_2_with_strategy.html#geometry.reference.algorithms.length.length_2_with_strategy.conformance">Conformance</a>
 162           </h6>
 163 <p>
 164             The function length implements function Length from the <a href="http://www.opengeospatial.org/standards/sfa" target="_top">OGC
 165             Simple Feature Specification</a>.
 166           </p>
 167 <h6>
 168 <a name="geometry.reference.algorithms.length.length_2_with_strategy.h6"></a>
 169             <span class="phrase"><a name="geometry.reference.algorithms.length.length_2_with_strategy.behavior"></a></span><a class="link" href="length_2_with_strategy.html#geometry.reference.algorithms.length.length_2_with_strategy.behavior">Behavior</a>
 170           </h6>
 171 <div class="informaltable"><table class="table">
 172 <colgroup>
 173 <col>
 174 <col>
 175 </colgroup>
 176 <thead><tr>
 177 <th>
 178                     <p>
 179                       Case
 180                     </p>
 181                   </th>
 182 <th>
 183                     <p>
 184                       Behavior
 185                     </p>
 186                   </th>
 187 </tr></thead>
 188 <tbody>
 189 <tr>
 190 <td>
 191                     <p>
 192                       pointlike (e.g. point)
 193                     </p>
 194                   </td>
 195 <td>
 196                     <p>
 197                       Returns 0
 198                     </p>
 199                   </td>
 200 </tr>
 201 <tr>
 202 <td>
 203                     <p>
 204                       linear (e.g. linestring)
 205                     </p>
 206                   </td>
 207 <td>
 208                     <p>
 209                       Returns the length
 210                     </p>
 211                   </td>
 212 </tr>
 213 <tr>
 214 <td>
 215                     <p>
 216                       areal (e.g. polygon)
 217                     </p>
 218                   </td>
 219 <td>
 220                     <p>
 221                       Returns 0
 222                     </p>
 223                   </td>
 224 </tr>
 225 </tbody>
 226 </table></div>
 227 <h6>
 228 <a name="geometry.reference.algorithms.length.length_2_with_strategy.h7"></a>
 229             <span class="phrase"><a name="geometry.reference.algorithms.length.length_2_with_strategy.complexity"></a></span><a class="link" href="length_2_with_strategy.html#geometry.reference.algorithms.length.length_2_with_strategy.complexity">Complexity</a>
 230           </h6>
 231 <p>
 232             Linear
 233           </p>
 234 <h6>
 235 <a name="geometry.reference.algorithms.length.length_2_with_strategy.h8"></a>
 236             <span class="phrase"><a name="geometry.reference.algorithms.length.length_2_with_strategy.examples"></a></span><a class="link" href="length_2_with_strategy.html#geometry.reference.algorithms.length.length_2_with_strategy.examples">Examples</a>
 237           </h6>
 238 <p>
 239             The following example shows the length measured over a sphere, expressed
 240             in kilometers. To do that the radius of the sphere must be specified
 241             in the constructor of the strategy.
 242           </p>
 243 <p>
 244 </p>
 245 <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span>
 246 <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>
 247 <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>
 248
 249 <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
 250 <span class="special">{</span>
 251     <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">;</span>
 252     <span class="keyword">typedef</span> <span class="identifier">model</span><span class="special">::</span><span class="identifier">point</span><span class="special">&lt;</span><span class="keyword">float</span><span class="special">,</span> <span class="number">2</span><span class="special">,</span> <span class="identifier">cs</span><span class="special">::</span><span class="identifier">spherical_equatorial</span><span class="special">&lt;</span><span class="identifier">degree</span><span class="special">&gt;</span> <span class="special">&gt;</span> <span class="identifier">P</span><span class="special">;</span>
 253     <span class="identifier">model</span><span class="special">::</span><span class="identifier">linestring</span><span class="special">&lt;</span><span class="identifier">P</span><span class="special">&gt;</span> <span class="identifier">line</span><span class="special">;</span>
 254     <span class="identifier">line</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="identifier">P</span><span class="special">(</span><span class="number">2</span><span class="special">,</span> <span class="number">41</span><span class="special">));</span>
 255     <span class="identifier">line</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="identifier">P</span><span class="special">(</span><span class="number">2</span><span class="special">,</span> <span class="number">48</span><span class="special">));</span>
 256     <span class="identifier">line</span><span class="special">.</span><span class="identifier">push_back</span><span class="special">(</span><span class="identifier">P</span><span class="special">(</span><span class="number">5</span><span class="special">,</span> <span class="number">52</span><span class="special">));</span>
 257     <span class="keyword">double</span> <span class="keyword">const</span> <span class="identifier">mean_radius</span> <span class="special">=</span> <span class="number">6371.0</span><span class="special">;</span> <a class="co" name="geometry.reference.algorithms.length.length_2_with_strategy.c0" href="length_2_with_strategy.html#geometry.reference.algorithms.length.length_2_with_strategy.c1"><img src="../../../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a>
 258     <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"length is "</span>
 259         <span class="special">&lt;&lt;</span> <span class="identifier">length</span><span class="special">(</span><span class="identifier">line</span><span class="special">,</span> <span class="identifier">strategy</span><span class="special">::</span><span class="identifier">distance</span><span class="special">::</span><span class="identifier">haversine</span><span class="special">&lt;</span><span class="keyword">float</span><span class="special">&gt;(</span><span class="identifier">mean_radius</span><span class="special">)</span> <span class="special">)</span>
 260         <span class="special">&lt;&lt;</span> <span class="string">" kilometers "</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>
 261
 262     <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
 263 <span class="special">}</span>
 264 </pre>
 265 <p>
 266           </p>
 267 <div class="calloutlist"><table border="0" summary="Callout list"><tr>
 268 <td width="5%" valign="top" align="left"><p><a name="geometry.reference.algorithms.length.length_2_with_strategy.c1"></a><a href="#geometry.reference.algorithms.length.length_2_with_strategy.c0"><img src="../../../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a> </p></td>
 269 <td valign="top" align="left"><p>
 270                 <a href="http://en.wikipedia.org/wiki/Earth_radius" target="_top">Wiki</a>
 271               </p></td>
 272 </tr></table></div>
 273 <p>
 274             Output:
 275           </p>
 276 <pre class="programlisting">length is 1272.03 kilometers
 277 </pre>
 278 </div>
 279 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 280 <td align="left"></td>
 281 <td align="right"><div class="copyright-footer">Copyright &#169; 2009-2017 Barend
 282       Gehrels, Bruno Lalande, Mateusz Loskot, Adam Wulkiewicz, Oracle and/or its
 283       affiliates<p>
 284         Distributed under the Boost Software License, Version 1.0. (See accompanying
 285         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>)
 286       </p>
 287 </div></td>
 288 </tr></table>
 289 <hr>
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