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  25 <div class="section">
  26 <div class="titlepage"><div><div><h5 class="title">
  27 <a name="geometry.reference.algorithms.union_.union__3"></a><a class="link" href="union__3.html" title="union_">union_</a>
  28 </h5></div></div></div>
  29 <p>
  30             <a class="indexterm" name="idm46186990100272"></a>
  31 Combines two geometries which each other.
  32           </p>
  33 <h6>
  34 <a name="geometry.reference.algorithms.union_.union__3.h0"></a>
  35             <span class="phrase"><a name="geometry.reference.algorithms.union_.union__3.description"></a></span><a class="link" href="union__3.html#geometry.reference.algorithms.union_.union__3.description">Description</a>
  36           </h6>
  37 <p>
  38             The free function union calculates the spatial set theoretic union of
  39             two geometries.
  40           </p>
  41 <h6>
  42 <a name="geometry.reference.algorithms.union_.union__3.h1"></a>
  43             <span class="phrase"><a name="geometry.reference.algorithms.union_.union__3.synopsis"></a></span><a class="link" href="union__3.html#geometry.reference.algorithms.union_.union__3.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">Geometry1</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Geometry2</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Collection</span><span class="special">&gt;</span>
  48 <span class="keyword">void</span> <span class="identifier">union_</span><span class="special">(</span><span class="identifier">Geometry1</span> <span class="keyword">const</span> <span class="special">&amp;</span> <span class="identifier">geometry1</span><span class="special">,</span> <span class="identifier">Geometry2</span> <span class="keyword">const</span> <span class="special">&amp;</span> <span class="identifier">geometry2</span><span class="special">,</span> <span class="identifier">Collection</span> <span class="special">&amp;</span> <span class="identifier">output_collection</span><span class="special">)</span></pre>
  49 <p>
  50           </p>
  51 <h6>
  52 <a name="geometry.reference.algorithms.union_.union__3.h2"></a>
  53             <span class="phrase"><a name="geometry.reference.algorithms.union_.union__3.parameters"></a></span><a class="link" href="union__3.html#geometry.reference.algorithms.union_.union__3.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                       Geometry1 const &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                       geometry1
  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                       Geometry2 const &amp;
 111                     </p>
 112                   </td>
 113 <td>
 114                     <p>
 115                       Any type fulfilling a Geometry Concept
 116                     </p>
 117                   </td>
 118 <td>
 119                     <p>
 120                       geometry2
 121                     </p>
 122                   </td>
 123 <td>
 124                     <p>
 125                       A model of the specified concept
 126                     </p>
 127                   </td>
 128 </tr>
 129 <tr>
 130 <td>
 131                     <p>
 132                       Collection &amp;
 133                     </p>
 134                   </td>
 135 <td>
 136                     <p>
 137                       output collection, either a multi-geometry, or a std::vector&lt;Geometry&gt;
 138                       / std::deque&lt;Geometry&gt; etc
 139                     </p>
 140                   </td>
 141 <td>
 142                     <p>
 143                       output_collection
 144                     </p>
 145                   </td>
 146 <td>
 147                     <p>
 148                       the output collection
 149                     </p>
 150                   </td>
 151 </tr>
 152 </tbody>
 153 </table></div>
 154 <h6>
 155 <a name="geometry.reference.algorithms.union_.union__3.h3"></a>
 156             <span class="phrase"><a name="geometry.reference.algorithms.union_.union__3.header"></a></span><a class="link" href="union__3.html#geometry.reference.algorithms.union_.union__3.header">Header</a>
 157           </h6>
 158 <p>
 159             Either
 160           </p>
 161 <p>
 162             <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>
 163           </p>
 164 <p>
 165             Or
 166           </p>
 167 <p>
 168             <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="keyword">union</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
 169           </p>
 170 <h6>
 171 <a name="geometry.reference.algorithms.union_.union__3.h4"></a>
 172             <span class="phrase"><a name="geometry.reference.algorithms.union_.union__3.conformance"></a></span><a class="link" href="union__3.html#geometry.reference.algorithms.union_.union__3.conformance">Conformance</a>
 173           </h6>
 174 <p>
 175             The function union implements function Union from the <a href="http://www.opengeospatial.org/standards/sfa" target="_top">OGC
 176             Simple Feature Specification</a>.
 177           </p>
 178 <div class="note"><table border="0" summary="Note">
 179 <tr>
 180 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../../../doc/src/images/note.png"></td>
 181 <th align="left">Note</th>
 182 </tr>
 183 <tr><td align="left" valign="top"><p>
 184               Boost.Geometry adds an underscore to avoid using the <code class="computeroutput"><span class="keyword">union</span></code> keyword
 185             </p></td></tr>
 186 </table></div>
 187 <h6>
 188 <a name="geometry.reference.algorithms.union_.union__3.h5"></a>
 189             <span class="phrase"><a name="geometry.reference.algorithms.union_.union__3.behavior"></a></span><a class="link" href="union__3.html#geometry.reference.algorithms.union_.union__3.behavior">Behavior</a>
 190           </h6>
 191 <div class="informaltable"><table class="table">
 192 <colgroup>
 193 <col>
 194 <col>
 195 </colgroup>
 196 <thead><tr>
 197 <th>
 198                     <p>
 199                       Case
 200                     </p>
 201                   </th>
 202 <th>
 203                     <p>
 204                       Behavior
 205                     </p>
 206                   </th>
 207 </tr></thead>
 208 <tbody>
 209 <tr>
 210 <td>
 211                     <p>
 212                       GeometryOut is a Point
 213                     </p>
 214                   </td>
 215 <td>
 216                     <p>
 217                       Calculates union linestrings of input (multi)points
 218                     </p>
 219                   </td>
 220 </tr>
 221 <tr>
 222 <td>
 223                     <p>
 224                       GeometryOut is a Linestring
 225                     </p>
 226                   </td>
 227 <td>
 228                     <p>
 229                       Calculates union linestrings of input (multi)linestrings
 230                     </p>
 231                   </td>
 232 </tr>
 233 <tr>
 234 <td>
 235                     <p>
 236                       GeometryOut is a Polygon
 237                     </p>
 238                   </td>
 239 <td>
 240                     <p>
 241                       Calculates union polygons of input (multi)polygons and/or boxes
 242                     </p>
 243                   </td>
 244 </tr>
 245 </tbody>
 246 </table></div>
 247 <div class="note"><table border="0" summary="Note">
 248 <tr>
 249 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../../../doc/src/images/note.png"></td>
 250 <th align="left">Note</th>
 251 </tr>
 252 <tr><td align="left" valign="top"><p>
 253               Check the <a class="link" href="../../concepts/concept_polygon.html" title="Polygon Concept">Polygon
 254               Concept</a> for the rules that polygon input for this algorithm
 255               should fulfill
 256             </p></td></tr>
 257 </table></div>
 258 <h6>
 259 <a name="geometry.reference.algorithms.union_.union__3.h6"></a>
 260             <span class="phrase"><a name="geometry.reference.algorithms.union_.union__3.example"></a></span><a class="link" href="union__3.html#geometry.reference.algorithms.union_.union__3.example">Example</a>
 261           </h6>
 262 <p>
 263             Shows how to get a united geometry of two polygons
 264           </p>
 265 <p>
 266 </p>
 267 <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span>
 268 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">vector</span><span class="special">&gt;</span>
 269
 270 <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>
 271 <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>
 272 <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">polygon</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 273
 274 <span class="preprocessor">#include</span> <span class="special">&lt;</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">&gt;</span>
 275
 276
 277 <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
 278 <span class="special">{</span>
 279     <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">polygon</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">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="special">&gt;</span> <span class="identifier">polygon</span><span class="special">;</span>
 280
 281     <span class="identifier">polygon</span> <span class="identifier">green</span><span class="special">,</span> <span class="identifier">blue</span><span class="special">;</span>
 282
 283     <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">read_wkt</span><span class="special">(</span>
 284         <span class="string">"POLYGON((2 1.3,2.4 1.7,2.8 1.8,3.4 1.2,3.7 1.6,3.4 2,4.1 3,5.3 2.6,5.4 1.2,4.9 0.8,2.9 0.7,2 1.3)"</span>
 285             <span class="string">"(4.0 2.0, 4.2 1.4, 4.8 1.9, 4.4 2.2, 4.0 2.0))"</span><span class="special">,</span> <span class="identifier">green</span><span class="special">);</span>
 286
 287     <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">read_wkt</span><span class="special">(</span>
 288         <span class="string">"POLYGON((4.0 -0.5 , 3.5 1.0 , 2.0 1.5 , 3.5 2.0 , 4.0 3.5 , 4.5 2.0 , 6.0 1.5 , 4.5 1.0 , 4.0 -0.5))"</span><span class="special">,</span> <span class="identifier">blue</span><span class="special">);</span>
 289
 290     <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span><span class="identifier">polygon</span><span class="special">&gt;</span> <span class="identifier">output</span><span class="special">;</span>
 291     <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">union_</span><span class="special">(</span><span class="identifier">green</span><span class="special">,</span> <span class="identifier">blue</span><span class="special">,</span> <span class="identifier">output</span><span class="special">);</span>
 292
 293     <span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span>
 294     <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"green || blue:"</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>
 295     <span class="identifier">BOOST_FOREACH</span><span class="special">(</span><span class="identifier">polygon</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">p</span><span class="special">,</span> <span class="identifier">output</span><span class="special">)</span>
 296     <span class="special">{</span>
 297         <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">i</span><span class="special">++</span> <span class="special">&lt;&lt;</span> <span class="string">": "</span> <span class="special">&lt;&lt;</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">area</span><span class="special">(</span><span class="identifier">p</span><span class="special">)</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>
 298     <span class="special">}</span>
 299
 300
 301     <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
 302 <span class="special">}</span>
 303 </pre>
 304 <p>
 305           </p>
 306 <p>
 307             Output:
 308           </p>
 309 <pre class="programlisting">green || blue:
 310 0: 5.64795
 311
 312 <img src="../../../../img/algorithms/union.png" alt="union">
 313
 314 </pre>
 315 <h6>
 316 <a name="geometry.reference.algorithms.union_.union__3.h7"></a>
 317             <span class="phrase"><a name="geometry.reference.algorithms.union_.union__3.see_also"></a></span><a class="link" href="union__3.html#geometry.reference.algorithms.union_.union__3.see_also">See
 318             also</a>
 319           </h6>
 320 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
 321 <li class="listitem">
 322                 <a class="link" href="../intersection.html" title="intersection">intersection</a>
 323               </li>
 324 <li class="listitem">
 325                 <a class="link" href="../difference.html" title="difference">difference</a>
 326               </li>
 327 <li class="listitem">
 328                 <a class="link" href="../sym_difference.html" title="sym_difference">sym_difference
 329                 (symmetric difference)</a>
 330               </li>
 331 </ul></div>
 332 </div>
 333 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 334 <td align="left"></td>
 335 <td align="right"><div class="copyright-footer">Copyright &#169; 2009-2019 Barend Gehrels, Bruno Lalande, Mateusz Loskot, Adam
 336       Wulkiewicz, Oracle and/or its affiliates<p>
 337         Distributed under the Boost Software License, Version 1.0. (See accompanying
 338         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>)
 339       </p>
 340 </div></td>
 341 </tr></table>
 342 <hr>
 343 <div class="spirit-nav">
 344 <a accesskey="p" href="union__4_with_strategy.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../union_.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="../unique.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a>
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