1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>for_each_segment</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="../for_each.html" title="for_each"> 9<link rel="prev" href="for_each_point.html" title="for_each_point"> 10<link rel="next" href="../intersection.html" title="intersection"> 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="for_each_point.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../for_each.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="../intersection.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 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="idm45635696171952"></a> 31Applies 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"><</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">></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">&</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 & 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"><</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> 140 </p> 141<p> 142 Or 143 </p> 144<p> 145 <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">for_each</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></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"><</span><span class="identifier">iostream</span><span class="special">></span> 169 170<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> 171<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">linestring</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 172<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">point_xy</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 173 174<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> 175 176 177<span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Segment</span><span class="special">></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"><</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"><</span><span class="identifier">Segment</span><span class="special">>::</span><span class="identifier">type</span><span class="special">,</span> 185 <span class="keyword">double</span> 186 <span class="special">>::</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">&</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"><</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">></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"><</span><span class="keyword">double</span><span class="special">></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"><</span><span class="identifier">point</span><span class="special">></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"><</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"><</span><span class="identifier">point</span><span class="special">></span> 225 <span class="special">></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"><<</span> <span class="string">"Min segment length: "</span> <span class="special"><<</span> <span class="identifier">functor</span><span class="special">.</span><span class="identifier">min_length</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span> 234 <span class="special"><<</span> <span class="string">"Max segment length: "</span> <span class="special"><<</span> <span class="identifier">functor</span><span class="special">.</span><span class="identifier">max_length</span> <span class="special"><<</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 245Max 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 © 2009-2019 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"> 259<a accesskey="p" href="for_each_point.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../for_each.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="../intersection.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 260</div> 261</body> 262</html> 263
