ceph/src/boost/libs/polygon/doc/gtl_custom_point.htm

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   7 <p><font face="Courier New">/*<br>
   8 Copyright 2008 Intel Corporation<br>
   9 <br>
  10 Use, modification and distribution are subject to the Boost Software License,<br>
  11 Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at<br>
  12 http://www.boost.org/LICENSE_1_0.txt).<br>
  13 */<br>
  14 #include &lt;boost/polygon/polygon.hpp&gt;<br>
  15 #include &lt;cassert&gt;<br>
  16 namespace gtl = boost::polygon;<br>
  17 using namespace boost::polygon::operators;<br><br>
  18 //lets make the body of main from point_usage.cpp<br>//a generic function parameterized by point type<br>template &lt;typename Point&gt;<br>void test_point() {<br>&nbsp;
  19 &nbsp; //constructing a gtl point<br>&nbsp; &nbsp;
  20 int x = 10;<br>&nbsp; &nbsp;
  21 int y = 20;<br>&nbsp; &nbsp;
  22 //Point pt(x, y);<br>&nbsp; &nbsp;
  23 Point pt = gtl::construct&lt;Point&gt;(x, y);<br>&nbsp; &nbsp;
  24 assert(gtl::x(pt) == 10);<br>&nbsp; &nbsp;
  25 assert(gtl::y(pt) == 20);<br>&nbsp; &nbsp;
  26 <br>&nbsp; &nbsp;
  27 //a quick primer in isotropic point access<br>&nbsp; &nbsp;
  28 typedef gtl::orientation_2d O;<br>&nbsp; &nbsp;
  29 using gtl::HORIZONTAL;<br>&nbsp; &nbsp;
  30 using gtl::VERTICAL;<br>&nbsp; &nbsp;
  31 O o = HORIZONTAL;<br>&nbsp; &nbsp;
  32 assert(gtl::x(pt) == gtl::get(pt, o));<br>&nbsp; &nbsp;
  33 <br>&nbsp; &nbsp;
  34 o = o.get_perpendicular();<br>&nbsp; &nbsp;
  35 assert(o == VERTICAL);<br>&nbsp; &nbsp;
  36 assert(gtl::y(pt) == gtl::get(pt, o));<br>&nbsp; &nbsp;
  37 <br>&nbsp; &nbsp;
  38 gtl::set(pt, o, 30);<br>&nbsp; &nbsp;
  39 assert(gtl::y(pt) == 30);<br>&nbsp; &nbsp;
  40 <br>&nbsp; &nbsp;
  41 //using some of the library functions<br>&nbsp; &nbsp;
  42 //Point pt2(10, 30);<br>&nbsp; &nbsp;
  43 Point pt2 = gtl::construct&lt;Point&gt;(10, 30);<br>&nbsp; &nbsp;
  44 assert(gtl::equivalence(pt, pt2));<br>&nbsp; &nbsp;
  45 <br>&nbsp; &nbsp;
  46 gtl::transformation&lt;int&gt; tr(gtl::axis_transformation::SWAP_XY);<br>&nbsp; &nbsp;
  47 gtl::transform(pt, tr);<br>&nbsp; &nbsp;
  48 assert(gtl::equivalence(pt, gtl::construct&lt;Point&gt;(30, 10)));<br>&nbsp; &nbsp;
  49 <br>&nbsp; &nbsp;
  50 gtl::transformation&lt;int&gt; tr2 = tr.inverse();<br>&nbsp; &nbsp;
  51 assert(tr == tr2); //SWAP_XY is its own inverse transform<br>&nbsp; &nbsp;
  52 <br>&nbsp; &nbsp;
  53 gtl::transform(pt, tr2);<br>&nbsp; &nbsp;
  54 assert(gtl::equivalence(pt, pt2)); //the two points are equal again<br>&nbsp; &nbsp;
  55 <br>&nbsp; &nbsp;
  56 gtl::move(pt, o, 10); //move pt 10 units in y<br>&nbsp; &nbsp;
  57 assert(gtl::euclidean_distance(pt, pt2) == 10.0f);<br>&nbsp; &nbsp;
  58 <br>&nbsp; &nbsp;
  59 gtl::move(pt, o.get_perpendicular(), 10); //move pt 10 units in x<br>&nbsp; &nbsp;
  60 assert(gtl::manhattan_distance(pt, pt2) == 20);<br>}<br>&nbsp; &nbsp;
  61 <br>//Now lets declare our own point type<br>//Bjarne says that if a class doesn't maintain an<br>//invariant just use a struct.<br>struct CPoint {<br>&nbsp; &nbsp;
  62 int x;<br>&nbsp; &nbsp;
  63 int y;<br>};<br>&nbsp; &nbsp;
  64 <br>//There, nice a simple...but wait, it doesn't do anything<br>//how do we use it to do all the things a point needs to do?<br>&nbsp; &nbsp;
  65 <br>&nbsp; &nbsp;
  66 <br>//First we register it as a point with boost polygon<br>namespace boost {
  67 namespace polygon {<br>&nbsp;&nbsp;&nbsp;
  68 template &lt;&gt;<br>&nbsp; &nbsp;
  69 struct geometry_concept&lt;CPoint&gt; { typedef point_concept type; };<br>&nbsp;<br>&nbsp; &nbsp;
  70 <br>&nbsp;&nbsp;&nbsp; //Then we specialize the gtl point traits for our point type<br>&nbsp; &nbsp;
  71 template &lt;&gt;<br>&nbsp; &nbsp;
  72 struct point_traits&lt;CPoint&gt; {<br>&nbsp; &nbsp;
  73 &nbsp; &nbsp;
  74 typedef int coordinate_type;<br>&nbsp; &nbsp;
  75 <br>&nbsp; &nbsp;
  76 &nbsp; &nbsp;
  77 static inline coordinate_type get(const CPoint&amp; point, <br>&nbsp; &nbsp;
  78 &nbsp; &nbsp;
  79 orientation_2d orient) {<br>&nbsp; &nbsp;
  80 &nbsp; &nbsp;
  81 &nbsp; &nbsp;
  82 if(orient == HORIZONTAL)<br>&nbsp; &nbsp;
  83 &nbsp; &nbsp;
  84 &nbsp; &nbsp;
  85 &nbsp; &nbsp;
  86 return point.x;<br>&nbsp; &nbsp;
  87 &nbsp; &nbsp;
  88 &nbsp; &nbsp;
  89 return point.y;<br>&nbsp; &nbsp;
  90 &nbsp; &nbsp;
  91 }<br>&nbsp; &nbsp;
  92 };<br>&nbsp; &nbsp;
  93 <br>&nbsp; &nbsp;
  94 template &lt;&gt;<br>&nbsp; &nbsp;
  95 struct point_mutable_traits&lt;CPoint&gt; {<br>
  96 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; typedef int coordinate_type;<br>
  97 <br>
  98 </font></p>
  99 <p><font face="Courier New">&nbsp; &nbsp;
 100 &nbsp; &nbsp;
 101 static inline void set(CPoint&amp; point, orientation_2d orient, int value) {<br>&nbsp; &nbsp;
 102 &nbsp; &nbsp;
 103 &nbsp; &nbsp;
 104 if(orient == HORIZONTAL)<br>&nbsp; &nbsp;
 105 &nbsp; &nbsp;
 106 &nbsp; &nbsp;
 107 &nbsp; &nbsp;
 108 point.x = value;<br>&nbsp; &nbsp;
 109 &nbsp; &nbsp;
 110 &nbsp; &nbsp;
 111 else<br>&nbsp; &nbsp;
 112 &nbsp; &nbsp;
 113 &nbsp; &nbsp;
 114 point.y = value;<br>&nbsp; &nbsp;
 115 &nbsp; &nbsp;
 116 }<br>&nbsp; &nbsp;
 117 &nbsp; &nbsp;
 118 static inline CPoint construct(int x_value, int y_value) {<br>&nbsp; &nbsp;
 119 &nbsp; &nbsp;
 120 &nbsp; &nbsp;
 121 CPoint retval;<br>&nbsp; &nbsp;
 122 &nbsp; &nbsp;
 123 &nbsp; &nbsp;
 124 retval.x = x_value;<br>&nbsp; &nbsp;
 125 &nbsp; &nbsp;
 126 &nbsp; &nbsp;
 127 retval.y = y_value; <br>&nbsp; &nbsp;
 128 &nbsp; &nbsp;
 129 &nbsp; &nbsp;
 130 return retval;<br>&nbsp; &nbsp;
 131 &nbsp; &nbsp;
 132 }<br>&nbsp; &nbsp;
 133 };<br>} }<br>&nbsp; &nbsp;
 134 <br>//Now lets see if the CPoint works with the library functions<br>int main() {<br>&nbsp; &nbsp;
 135 test_point&lt;CPoint&gt;(); //yay! All your testing is done for you.<br>&nbsp; &nbsp;
 136 return 0;<br>}<br>&nbsp; &nbsp;
 137 <br>//Now you know how to map a user type to the library point concept<br>//and how to write a generic function parameterized by point type<br>//using the library interfaces to access it.<br>&nbsp; &nbsp;
 138 &nbsp;</font></p>
 139
 140
 141
 142 <table class="docinfo" id="table1" frame="void" rules="none">
 143         <colgroup>
 144                 <col class="docinfo-name"><col class="docinfo-content">
 145         </colgroup>
 146         <tbody valign="top">
 147                 <tr>
 148                         <th class="docinfo-name">Copyright:</th>
 149                         <td>Copyright © Intel Corporation 2008-2010.</td>
 150                 </tr>
 151                 <tr class="field">
 152                         <th class="docinfo-name">License:</th>
 153                         <td class="field-body">Distributed under the Boost Software License,
 154                         Version 1.0. (See accompanying file <tt class="literal">
 155                         <span class="pre">LICENSE_1_0.txt</span></tt> or copy at
 156                         <a class="reference" target="_top" href="http://www.boost.org/LICENSE_1_0.txt">
 157                         http://www.boost.org/LICENSE_1_0.txt</a>)</td>
 158                 </tr>
 159 </tbody></table>
 160
 161 </body></html>