libs/geometry/doc/html/geometry/reference/algorithms/is_empty.html

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  26 <div class="titlepage"><div><div><h4 class="title">
  27 <a name="geometry.reference.algorithms.is_empty"></a><a class="link" href="is_empty.html" title="is_empty">is_empty</a>
  28 </h4></div></div></div>
  29 <p>
  30           <a class="indexterm" name="idm46186997276944"></a>
  31 Checks if a geometry is the empty set.
  32         </p>
  33 <h6>
  34 <a name="geometry.reference.algorithms.is_empty.h0"></a>
  35           <span class="phrase"><a name="geometry.reference.algorithms.is_empty.synopsis"></a></span><a class="link" href="is_empty.html#geometry.reference.algorithms.is_empty.synopsis">Synopsis</a>
  36         </h6>
  37 <p>
  38 </p>
  39 <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">&gt;</span>
  40 <span class="keyword">bool</span> <span class="identifier">is_empty</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></pre>
  41 <p>
  42         </p>
  43 <h6>
  44 <a name="geometry.reference.algorithms.is_empty.h1"></a>
  45           <span class="phrase"><a name="geometry.reference.algorithms.is_empty.parameters"></a></span><a class="link" href="is_empty.html#geometry.reference.algorithms.is_empty.parameters">Parameters</a>
  46         </h6>
  47 <div class="informaltable"><table class="table">
  48 <colgroup>
  49 <col>
  50 <col>
  51 <col>
  52 <col>
  53 </colgroup>
  54 <thead><tr>
  55 <th>
  56                   <p>
  57                     Type
  58                   </p>
  59                 </th>
  60 <th>
  61                   <p>
  62                     Concept
  63                   </p>
  64                 </th>
  65 <th>
  66                   <p>
  67                     Name
  68                   </p>
  69                 </th>
  70 <th>
  71                   <p>
  72                     Description
  73                   </p>
  74                 </th>
  75 </tr></thead>
  76 <tbody><tr>
  77 <td>
  78                   <p>
  79                     Geometry const &amp;
  80                   </p>
  81                 </td>
  82 <td>
  83                   <p>
  84                     Any type fulfilling a Geometry Concept
  85                   </p>
  86                 </td>
  87 <td>
  88                   <p>
  89                     geometry
  90                   </p>
  91                 </td>
  92 <td>
  93                   <p>
  94                     A model of the specified concept
  95                   </p>
  96                 </td>
  97 </tr></tbody>
  98 </table></div>
  99 <h6>
 100 <a name="geometry.reference.algorithms.is_empty.h2"></a>
 101           <span class="phrase"><a name="geometry.reference.algorithms.is_empty.returns"></a></span><a class="link" href="is_empty.html#geometry.reference.algorithms.is_empty.returns">Returns</a>
 102         </h6>
 103 <p>
 104           Returns true if the geometry is the empty set
 105         </p>
 106 <h6>
 107 <a name="geometry.reference.algorithms.is_empty.h3"></a>
 108           <span class="phrase"><a name="geometry.reference.algorithms.is_empty.header"></a></span><a class="link" href="is_empty.html#geometry.reference.algorithms.is_empty.header">Header</a>
 109         </h6>
 110 <p>
 111           Either
 112         </p>
 113 <p>
 114           <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>
 115         </p>
 116 <p>
 117           Or
 118         </p>
 119 <p>
 120           <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">is_empty</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
 121         </p>
 122 <h6>
 123 <a name="geometry.reference.algorithms.is_empty.h4"></a>
 124           <span class="phrase"><a name="geometry.reference.algorithms.is_empty.conformance"></a></span><a class="link" href="is_empty.html#geometry.reference.algorithms.is_empty.conformance">Conformance</a>
 125         </h6>
 126 <p>
 127           The function is_empty implements function IsEmpty from the <a href="http://www.opengeospatial.org/standards/sfa" target="_top">OGC
 128           Simple Feature Specification</a>.
 129         </p>
 130 <h6>
 131 <a name="geometry.reference.algorithms.is_empty.h5"></a>
 132           <span class="phrase"><a name="geometry.reference.algorithms.is_empty.supported_geometries"></a></span><a class="link" href="is_empty.html#geometry.reference.algorithms.is_empty.supported_geometries">Supported
 133           geometries</a>
 134         </h6>
 135 <div class="informaltable"><table class="table">
 136 <colgroup>
 137 <col>
 138 <col>
 139 </colgroup>
 140 <thead><tr>
 141 <th>
 142                   <p>
 143                     Geometry
 144                   </p>
 145                 </th>
 146 <th>
 147                   <p>
 148                     Status
 149                   </p>
 150                 </th>
 151 </tr></thead>
 152 <tbody>
 153 <tr>
 154 <td>
 155                   <p>
 156                     Point
 157                   </p>
 158                 </td>
 159 <td>
 160                   <p>
 161                     <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span>
 162                   </p>
 163                 </td>
 164 </tr>
 165 <tr>
 166 <td>
 167                   <p>
 168                     Segment
 169                   </p>
 170                 </td>
 171 <td>
 172                   <p>
 173                     <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span>
 174                   </p>
 175                 </td>
 176 </tr>
 177 <tr>
 178 <td>
 179                   <p>
 180                     Box
 181                   </p>
 182                 </td>
 183 <td>
 184                   <p>
 185                     <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span>
 186                   </p>
 187                 </td>
 188 </tr>
 189 <tr>
 190 <td>
 191                   <p>
 192                     Linestring
 193                   </p>
 194                 </td>
 195 <td>
 196                   <p>
 197                     <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span>
 198                   </p>
 199                 </td>
 200 </tr>
 201 <tr>
 202 <td>
 203                   <p>
 204                     Ring
 205                   </p>
 206                 </td>
 207 <td>
 208                   <p>
 209                     <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span>
 210                   </p>
 211                 </td>
 212 </tr>
 213 <tr>
 214 <td>
 215                   <p>
 216                     Polygon
 217                   </p>
 218                 </td>
 219 <td>
 220                   <p>
 221                     <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span>
 222                   </p>
 223                 </td>
 224 </tr>
 225 <tr>
 226 <td>
 227                   <p>
 228                     MultiPoint
 229                   </p>
 230                 </td>
 231 <td>
 232                   <p>
 233                     <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span>
 234                   </p>
 235                 </td>
 236 </tr>
 237 <tr>
 238 <td>
 239                   <p>
 240                     MultiLinestring
 241                   </p>
 242                 </td>
 243 <td>
 244                   <p>
 245                     <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span>
 246                   </p>
 247                 </td>
 248 </tr>
 249 <tr>
 250 <td>
 251                   <p>
 252                     MultiPolygon
 253                   </p>
 254                 </td>
 255 <td>
 256                   <p>
 257                     <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span>
 258                   </p>
 259                 </td>
 260 </tr>
 261 <tr>
 262 <td>
 263                   <p>
 264                     Variant
 265                   </p>
 266                 </td>
 267 <td>
 268                   <p>
 269                     <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span>
 270                   </p>
 271                 </td>
 272 </tr>
 273 </tbody>
 274 </table></div>
 275 <h6>
 276 <a name="geometry.reference.algorithms.is_empty.h6"></a>
 277           <span class="phrase"><a name="geometry.reference.algorithms.is_empty.complexity"></a></span><a class="link" href="is_empty.html#geometry.reference.algorithms.is_empty.complexity">Complexity</a>
 278         </h6>
 279 <p>
 280           Constant-time
 281         </p>
 282 <h6>
 283 <a name="geometry.reference.algorithms.is_empty.h7"></a>
 284           <span class="phrase"><a name="geometry.reference.algorithms.is_empty.example"></a></span><a class="link" href="is_empty.html#geometry.reference.algorithms.is_empty.example">Example</a>
 285         </h6>
 286 <p>
 287           Check if a geometry is the empty set
 288         </p>
 289 <p>
 290 </p>
 291 <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span>
 292
 293 <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>
 294 <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>
 295
 296
 297 <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
 298 <span class="special">{</span>
 299     <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">multi_linestring</span>
 300         <span class="special">&lt;</span>
 301             <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>
 302                 <span class="special">&lt;</span>
 303                     <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>
 304                 <span class="special">&gt;</span>
 305         <span class="special">&gt;</span> <span class="identifier">mls</span><span class="special">;</span>
 306     <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><span class="string">"MULTILINESTRING((0 0,0 10,10 0),(1 1,8 1,1 8))"</span><span class="special">,</span> <span class="identifier">mls</span><span class="special">);</span>
 307     <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"Is empty? "</span> <span class="special">&lt;&lt;</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">is_empty</span><span class="special">(</span><span class="identifier">mls</span><span class="special">)</span> <span class="special">?</span> <span class="string">"yes"</span> <span class="special">:</span> <span class="string">"no"</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>
 308     <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">clear</span><span class="special">(</span><span class="identifier">mls</span><span class="special">);</span>
 309     <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"Is empty (after clearing)? "</span> <span class="special">&lt;&lt;</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">is_empty</span><span class="special">(</span><span class="identifier">mls</span><span class="special">)</span> <span class="special">?</span> <span class="string">"yes"</span> <span class="special">:</span> <span class="string">"no"</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>
 310     <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
 311 <span class="special">}</span>
 312 </pre>
 313 <p>
 314         </p>
 315 <p>
 316           Output:
 317         </p>
 318 <pre class="programlisting">Is empty? no
 319 Is empty (after clearing)? yes
 320 </pre>
 321 <h6>
 322 <a name="geometry.reference.algorithms.is_empty.h8"></a>
 323           <span class="phrase"><a name="geometry.reference.algorithms.is_empty.see_also"></a></span><a class="link" href="is_empty.html#geometry.reference.algorithms.is_empty.see_also">See
 324           also</a>
 325         </h6>
 326 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
 327               <a class="link" href="num_points.html" title="num_points">num_points</a>
 328             </li></ul></div>
 329 </div>
 330 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 331 <td align="left"></td>
 332 <td align="right"><div class="copyright-footer">Copyright &#169; 2009-2019 Barend Gehrels, Bruno Lalande, Mateusz Loskot, Adam
 333       Wulkiewicz, Oracle and/or its affiliates<p>
 334         Distributed under the Boost Software License, Version 1.0. (See accompanying
 335         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>)
 336       </p>
 337 </div></td>
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