1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>clear</title> 5<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../../index.html" title="Chapter 1. Geometry"> 8<link rel="up" href="../algorithms.html" title="Algorithms"> 9<link rel="prev" href="centroid/return_centroid_2_with_strategy.html" title="return_centroid (with strategy)"> 10<link rel="next" href="convert.html" title="convert"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="centroid/return_centroid_2_with_strategy.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../algorithms.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="convert.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h4 class="title"> 27<a name="geometry.reference.algorithms.clear"></a><a class="link" href="clear.html" title="clear">clear</a> 28</h4></div></div></div> 29<p> 30 <a class="indexterm" name="idm45635705026400"></a> 31Clears a linestring, ring or polygon (exterior+interiors) or multi*. 32 </p> 33<h6> 34<a name="geometry.reference.algorithms.clear.h0"></a> 35 <span class="phrase"><a name="geometry.reference.algorithms.clear.description"></a></span><a class="link" href="clear.html#geometry.reference.algorithms.clear.description">Description</a> 36 </h6> 37<p> 38 Generic function to clear a geometry. All points will be removed from the 39 collection or collections making up the geometry. In most cases this is 40 equivalent to the .clear() method of a std::vector<...>. In the case 41 of a polygon, this clear functionality is automatically called for the 42 exterior ring, and for the interior ring collection. In the case of a point, 43 boxes and segments, nothing will happen. 44 </p> 45<h6> 46<a name="geometry.reference.algorithms.clear.h1"></a> 47 <span class="phrase"><a name="geometry.reference.algorithms.clear.synopsis"></a></span><a class="link" href="clear.html#geometry.reference.algorithms.clear.synopsis">Synopsis</a> 48 </h6> 49<p> 50</p> 51<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Geometry</span><span class="special">></span> 52<span class="keyword">void</span> <span class="identifier">clear</span><span class="special">(</span><span class="identifier">Geometry</span> <span class="special">&</span> <span class="identifier">geometry</span><span class="special">)</span></pre> 53<p> 54 </p> 55<h6> 56<a name="geometry.reference.algorithms.clear.h2"></a> 57 <span class="phrase"><a name="geometry.reference.algorithms.clear.parameters"></a></span><a class="link" href="clear.html#geometry.reference.algorithms.clear.parameters">Parameters</a> 58 </h6> 59<div class="informaltable"><table class="table"> 60<colgroup> 61<col> 62<col> 63<col> 64<col> 65</colgroup> 66<thead><tr> 67<th> 68 <p> 69 Type 70 </p> 71 </th> 72<th> 73 <p> 74 Concept 75 </p> 76 </th> 77<th> 78 <p> 79 Name 80 </p> 81 </th> 82<th> 83 <p> 84 Description 85 </p> 86 </th> 87</tr></thead> 88<tbody><tr> 89<td> 90 <p> 91 Geometry & 92 </p> 93 </td> 94<td> 95 <p> 96 Any type fulfilling a Geometry Concept 97 </p> 98 </td> 99<td> 100 <p> 101 geometry 102 </p> 103 </td> 104<td> 105 <p> 106 A model of the specified concept which will be cleared 107 </p> 108 </td> 109</tr></tbody> 110</table></div> 111<h6> 112<a name="geometry.reference.algorithms.clear.h3"></a> 113 <span class="phrase"><a name="geometry.reference.algorithms.clear.header"></a></span><a class="link" href="clear.html#geometry.reference.algorithms.clear.header">Header</a> 114 </h6> 115<p> 116 Either 117 </p> 118<p> 119 <code class="computeroutput"><span class="preprocessor">#include</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">hpp</span><span class="special">></span></code> 120 </p> 121<p> 122 Or 123 </p> 124<p> 125 <code class="computeroutput"><span class="preprocessor">#include</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">algorithms</span><span class="special">/</span><span class="identifier">clear</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code> 126 </p> 127<h6> 128<a name="geometry.reference.algorithms.clear.h4"></a> 129 <span class="phrase"><a name="geometry.reference.algorithms.clear.conformance"></a></span><a class="link" href="clear.html#geometry.reference.algorithms.clear.conformance">Conformance</a> 130 </h6> 131<p> 132 The function clear is not defined by OGC. 133 </p> 134<p> 135 The function clear conforms to the clear() method of the C++ std-library. 136 </p> 137<h6> 138<a name="geometry.reference.algorithms.clear.h5"></a> 139 <span class="phrase"><a name="geometry.reference.algorithms.clear.supported_geometries"></a></span><a class="link" href="clear.html#geometry.reference.algorithms.clear.supported_geometries">Supported 140 geometries</a> 141 </h6> 142<div class="informaltable"><table class="table"> 143<colgroup> 144<col> 145<col> 146</colgroup> 147<thead><tr> 148<th> 149 <p> 150 Geometry 151 </p> 152 </th> 153<th> 154 <p> 155 Status 156 </p> 157 </th> 158</tr></thead> 159<tbody> 160<tr> 161<td> 162 <p> 163 Point 164 </p> 165 </td> 166<td> 167 <p> 168 <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span> 169 </p> 170 </td> 171</tr> 172<tr> 173<td> 174 <p> 175 Segment 176 </p> 177 </td> 178<td> 179 <p> 180 <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span> 181 </p> 182 </td> 183</tr> 184<tr> 185<td> 186 <p> 187 Box 188 </p> 189 </td> 190<td> 191 <p> 192 <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span> 193 </p> 194 </td> 195</tr> 196<tr> 197<td> 198 <p> 199 Linestring 200 </p> 201 </td> 202<td> 203 <p> 204 <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span> 205 </p> 206 </td> 207</tr> 208<tr> 209<td> 210 <p> 211 Ring 212 </p> 213 </td> 214<td> 215 <p> 216 <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span> 217 </p> 218 </td> 219</tr> 220<tr> 221<td> 222 <p> 223 Polygon 224 </p> 225 </td> 226<td> 227 <p> 228 <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span> 229 </p> 230 </td> 231</tr> 232<tr> 233<td> 234 <p> 235 MultiPoint 236 </p> 237 </td> 238<td> 239 <p> 240 <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span> 241 </p> 242 </td> 243</tr> 244<tr> 245<td> 246 <p> 247 MultiLinestring 248 </p> 249 </td> 250<td> 251 <p> 252 <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span> 253 </p> 254 </td> 255</tr> 256<tr> 257<td> 258 <p> 259 MultiPolygon 260 </p> 261 </td> 262<td> 263 <p> 264 <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span> 265 </p> 266 </td> 267</tr> 268<tr> 269<td> 270 <p> 271 Variant 272 </p> 273 </td> 274<td> 275 <p> 276 <span class="inlinemediaobject"><img src="../../../img/ok.png" alt="ok"></span> 277 </p> 278 </td> 279</tr> 280</tbody> 281</table></div> 282<h6> 283<a name="geometry.reference.algorithms.clear.h6"></a> 284 <span class="phrase"><a name="geometry.reference.algorithms.clear.behavior"></a></span><a class="link" href="clear.html#geometry.reference.algorithms.clear.behavior">Behavior</a> 285 </h6> 286<div class="informaltable"><table class="table"> 287<colgroup> 288<col> 289<col> 290</colgroup> 291<thead><tr> 292<th> 293 <p> 294 Case 295 </p> 296 </th> 297<th> 298 <p> 299 Behavior 300 </p> 301 </th> 302</tr></thead> 303<tbody> 304<tr> 305<td> 306 <p> 307 Point 308 </p> 309 </td> 310<td> 311 <p> 312 Nothing happens, geometry is unchanged 313 </p> 314 </td> 315</tr> 316<tr> 317<td> 318 <p> 319 Segment 320 </p> 321 </td> 322<td> 323 <p> 324 Nothing happens, geometry is unchanged 325 </p> 326 </td> 327</tr> 328<tr> 329<td> 330 <p> 331 Box 332 </p> 333 </td> 334<td> 335 <p> 336 Nothing happens, geometry is unchanged 337 </p> 338 </td> 339</tr> 340<tr> 341<td> 342 <p> 343 Linestring 344 </p> 345 </td> 346<td> 347 <p> 348 Linestring is cleared 349 </p> 350 </td> 351</tr> 352<tr> 353<td> 354 <p> 355 Ring 356 </p> 357 </td> 358<td> 359 <p> 360 Ring is cleared 361 </p> 362 </td> 363</tr> 364<tr> 365<td> 366 <p> 367 Polygon 368 </p> 369 </td> 370<td> 371 <p> 372 The exterior ring is cleared and all interior rings are removed 373 </p> 374 </td> 375</tr> 376<tr> 377<td> 378 <p> 379 Multi Point 380 </p> 381 </td> 382<td> 383 <p> 384 Multi Point is cleared 385 </p> 386 </td> 387</tr> 388<tr> 389<td> 390 <p> 391 Multi Linestring 392 </p> 393 </td> 394<td> 395 <p> 396 Multi Linestring is cleared 397 </p> 398 </td> 399</tr> 400<tr> 401<td> 402 <p> 403 Multi Polygon 404 </p> 405 </td> 406<td> 407 <p> 408 Multi Polygon is cleared 409 </p> 410 </td> 411</tr> 412</tbody> 413</table></div> 414<h6> 415<a name="geometry.reference.algorithms.clear.h7"></a> 416 <span class="phrase"><a name="geometry.reference.algorithms.clear.complexity"></a></span><a class="link" href="clear.html#geometry.reference.algorithms.clear.complexity">Complexity</a> 417 </h6> 418<p> 419 Constant 420 </p> 421<h6> 422<a name="geometry.reference.algorithms.clear.h8"></a> 423 <span class="phrase"><a name="geometry.reference.algorithms.clear.example"></a></span><a class="link" href="clear.html#geometry.reference.algorithms.clear.example">Example</a> 424 </h6> 425<p> 426 Shows how to clear a ring or polygon 427 </p> 428<p> 429</p> 430<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> 431 432<span class="preprocessor">#include</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">hpp</span><span class="special">></span> 433<span class="preprocessor">#include</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">geometries</span><span class="special">/</span><span class="identifier">polygon</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 434<span class="preprocessor">#include</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">geometries</span><span class="special">/</span><span class="identifier">ring</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 435<span class="preprocessor">#include</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">geometries</span><span class="special">/</span><span class="identifier">adapted</span><span class="special">/</span><span class="identifier">boost_tuple</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 436 437<span class="identifier">BOOST_GEOMETRY_REGISTER_BOOST_TUPLE_CS</span><span class="special">(</span><span class="identifier">cs</span><span class="special">::</span><span class="identifier">cartesian</span><span class="special">)</span> 438 439<span class="preprocessor">#include</span> <span class="special"><</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">></span> 440 441<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> 442<span class="special">{</span> 443 <span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">assign</span><span class="special">::</span><span class="identifier">tuple_list_of</span><span class="special">;</span> 444 445 <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">tuple</span><span class="special"><</span><span class="keyword">float</span><span class="special">,</span> <span class="keyword">float</span><span class="special">></span> <span class="identifier">point</span><span class="special">;</span> 446 <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"><</span><span class="identifier">point</span><span class="special">></span> <span class="identifier">polygon</span><span class="special">;</span> 447 <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">ring</span><span class="special"><</span><span class="identifier">point</span><span class="special">></span> <span class="identifier">ring</span><span class="special">;</span> 448 449 <span class="identifier">polygon</span> <span class="identifier">poly</span><span class="special">;</span> 450 451 <span class="comment">// Fill the polygon (using its own methods + Boost.Assign)</span> 452 <span class="identifier">poly</span><span class="special">.</span><span class="identifier">outer</span><span class="special">()</span> <span class="special">=</span> <span class="identifier">tuple_list_of</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="number">0</span><span class="special">,</span> <span class="number">9</span><span class="special">)(</span><span class="number">10</span><span class="special">,</span> <span class="number">10</span><span class="special">)(</span><span class="number">0</span><span class="special">,</span> <span class="number">0</span><span class="special">);</span> 453 <span class="identifier">poly</span><span class="special">.</span><span class="identifier">inners</span><span class="special">().</span><span class="identifier">push_back</span><span class="special">(</span><span class="identifier">tuple_list_of</span><span class="special">(</span><span class="number">1</span><span class="special">,</span> <span class="number">2</span><span class="special">)(</span><span class="number">4</span><span class="special">,</span> <span class="number">6</span><span class="special">)(</span><span class="number">2</span><span class="special">,</span> <span class="number">8</span><span class="special">)(</span><span class="number">1</span><span class="special">,</span> <span class="number">2</span><span class="special">));</span> 454 455 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</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">dsv</span><span class="special">(</span><span class="identifier">poly</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 456 <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">poly</span><span class="special">);</span> 457 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</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">dsv</span><span class="special">(</span><span class="identifier">poly</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 458 459 <span class="comment">// Create a ring using Boost.Assign</span> 460 <span class="identifier">ring</span> <span class="identifier">r</span> <span class="special">=</span> <span class="identifier">tuple_list_of</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="number">0</span><span class="special">,</span> <span class="number">9</span><span class="special">)(</span><span class="number">8</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="number">0</span><span class="special">);</span> 461 462 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</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">dsv</span><span class="special">(</span><span class="identifier">r</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 463 <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">r</span><span class="special">);</span> 464 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</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">dsv</span><span class="special">(</span><span class="identifier">r</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> 465 466 <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> 467<span class="special">}</span> 468</pre> 469<p> 470 </p> 471<p> 472 Output: 473 </p> 474<pre class="programlisting">(((0, 0), (0, 10), (11, 11), (0, 0)), ((0, 0), (0, 10), (11, 11), (0, 0))) 475(()) 476((0, 0), (0, 9), (8, 8), (0, 0)) 477() 478</pre> 479</div> 480<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 481<td align="left"></td> 482<td align="right"><div class="copyright-footer">Copyright © 2009-2019 Barend Gehrels, Bruno Lalande, Mateusz Loskot, Adam 483 Wulkiewicz, Oracle and/or its affiliates<p> 484 Distributed under the Boost Software License, Version 1.0. (See accompanying 485 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>) 486 </p> 487</div></td> 488</tr></table> 489<hr> 490<div class="spirit-nav"> 491<a accesskey="p" href="centroid/return_centroid_2_with_strategy.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../algorithms.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="convert.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 492</div> 493</body> 494</html> 495
