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<meta http-equiv="Content-Type" content="text/html; charset=windows-1252"><title>Custom Point</title></head><body>

<p><font face="Courier New">/*<br>
Copyright 2008 Intel Corporation<br>
<br>
Use, modification and distribution are subject to the Boost Software License,<br>
Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at<br>
http://www.boost.org/LICENSE_1_0.txt).<br>
*/<br>
#include &lt;boost/polygon/polygon.hpp&gt;<br>
#include &lt;cassert&gt;<br>
namespace gtl = boost::polygon;<br>
using namespace boost::polygon::operators;<br><br>
//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; 
&nbsp; //constructing a gtl point<br>&nbsp; &nbsp; 
int x = 10;<br>&nbsp; &nbsp; 
int y = 20;<br>&nbsp; &nbsp; 
//Point pt(x, y);<br>&nbsp; &nbsp; 
Point pt = gtl::construct&lt;Point&gt;(x, y);<br>&nbsp; &nbsp; 
assert(gtl::x(pt) == 10);<br>&nbsp; &nbsp; 
assert(gtl::y(pt) == 20);<br>&nbsp; &nbsp; 
<br>&nbsp; &nbsp; 
//a quick primer in isotropic point access<br>&nbsp; &nbsp; 
typedef gtl::orientation_2d O;<br>&nbsp; &nbsp; 
using gtl::HORIZONTAL;<br>&nbsp; &nbsp; 
using gtl::VERTICAL;<br>&nbsp; &nbsp; 
O o = HORIZONTAL;<br>&nbsp; &nbsp; 
assert(gtl::x(pt) == gtl::get(pt, o));<br>&nbsp; &nbsp; 
<br>&nbsp; &nbsp; 
o = o.get_perpendicular();<br>&nbsp; &nbsp; 
assert(o == VERTICAL);<br>&nbsp; &nbsp; 
assert(gtl::y(pt) == gtl::get(pt, o));<br>&nbsp; &nbsp; 
<br>&nbsp; &nbsp; 
gtl::set(pt, o, 30);<br>&nbsp; &nbsp; 
assert(gtl::y(pt) == 30);<br>&nbsp; &nbsp; 
<br>&nbsp; &nbsp; 
//using some of the library functions<br>&nbsp; &nbsp; 
//Point pt2(10, 30);<br>&nbsp; &nbsp; 
Point pt2 = gtl::construct&lt;Point&gt;(10, 30);<br>&nbsp; &nbsp; 
assert(gtl::equivalence(pt, pt2));<br>&nbsp; &nbsp; 
<br>&nbsp; &nbsp; 
gtl::transformation&lt;int&gt; tr(gtl::axis_transformation::SWAP_XY);<br>&nbsp; &nbsp; 
gtl::transform(pt, tr);<br>&nbsp; &nbsp; 
assert(gtl::equivalence(pt, gtl::construct&lt;Point&gt;(30, 10)));<br>&nbsp; &nbsp; 
<br>&nbsp; &nbsp; 
gtl::transformation&lt;int&gt; tr2 = tr.inverse();<br>&nbsp; &nbsp; 
assert(tr == tr2); //SWAP_XY is its own inverse transform<br>&nbsp; &nbsp; 
<br>&nbsp; &nbsp; 
gtl::transform(pt, tr2);<br>&nbsp; &nbsp; 
assert(gtl::equivalence(pt, pt2)); //the two points are equal again<br>&nbsp; &nbsp; 
<br>&nbsp; &nbsp; 
gtl::move(pt, o, 10); //move pt 10 units in y<br>&nbsp; &nbsp; 
assert(gtl::euclidean_distance(pt, pt2) == 10.0f);<br>&nbsp; &nbsp; 
<br>&nbsp; &nbsp; 
gtl::move(pt, o.get_perpendicular(), 10); //move pt 10 units in x<br>&nbsp; &nbsp; 
assert(gtl::manhattan_distance(pt, pt2) == 20);<br>}<br>&nbsp; &nbsp; 
<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; 
int x;<br>&nbsp; &nbsp; 
int y;<br>};<br>&nbsp; &nbsp; 
<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; 
<br>&nbsp; &nbsp; 
<br>//First we register it as a point with boost polygon<br>namespace boost { 
namespace polygon {<br>&nbsp;&nbsp;&nbsp; 
template &lt;&gt;<br>&nbsp; &nbsp; 
struct geometry_concept&lt;CPoint&gt; { typedef point_concept type; };<br>&nbsp;<br>&nbsp; &nbsp; 
<br>&nbsp;&nbsp;&nbsp; //Then we specialize the gtl point traits for our point type<br>&nbsp; &nbsp; 
template &lt;&gt;<br>&nbsp; &nbsp; 
struct point_traits&lt;CPoint&gt; {<br>&nbsp; &nbsp; 
&nbsp; &nbsp; 
typedef int coordinate_type;<br>&nbsp; &nbsp; 
<br>&nbsp; &nbsp; 
&nbsp; &nbsp; 
static inline coordinate_type get(const CPoint&amp; point, <br>&nbsp; &nbsp; 
&nbsp; &nbsp; 
orientation_2d orient) {<br>&nbsp; &nbsp; 
&nbsp; &nbsp; 
&nbsp; &nbsp; 
if(orient == HORIZONTAL)<br>&nbsp; &nbsp; 
&nbsp; &nbsp; 
&nbsp; &nbsp; 
&nbsp; &nbsp; 
return point.x;<br>&nbsp; &nbsp; 
&nbsp; &nbsp; 
&nbsp; &nbsp; 
return point.y;<br>&nbsp; &nbsp; 
&nbsp; &nbsp; 
}<br>&nbsp; &nbsp; 
};<br>&nbsp; &nbsp; 
<br>&nbsp; &nbsp; 
template &lt;&gt;<br>&nbsp; &nbsp; 
struct point_mutable_traits&lt;CPoint&gt; {<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; typedef int coordinate_type;<br>
<br>
</font></p>
<p><font face="Courier New">&nbsp; &nbsp; 
&nbsp; &nbsp; 
static inline void set(CPoint&amp; point, orientation_2d orient, int value) {<br>&nbsp; &nbsp; 
&nbsp; &nbsp; 
&nbsp; &nbsp; 
if(orient == HORIZONTAL)<br>&nbsp; &nbsp; 
&nbsp; &nbsp; 
&nbsp; &nbsp; 
&nbsp; &nbsp; 
point.x = value;<br>&nbsp; &nbsp; 
&nbsp; &nbsp; 
&nbsp; &nbsp; 
else<br>&nbsp; &nbsp; 
&nbsp; &nbsp; 
&nbsp; &nbsp; 
point.y = value;<br>&nbsp; &nbsp; 
&nbsp; &nbsp; 
}<br>&nbsp; &nbsp; 
&nbsp; &nbsp; 
static inline CPoint construct(int x_value, int y_value) {<br>&nbsp; &nbsp; 
&nbsp; &nbsp; 
&nbsp; &nbsp; 
CPoint retval;<br>&nbsp; &nbsp; 
&nbsp; &nbsp; 
&nbsp; &nbsp; 
retval.x = x_value;<br>&nbsp; &nbsp; 
&nbsp; &nbsp; 
&nbsp; &nbsp; 
retval.y = y_value; <br>&nbsp; &nbsp; 
&nbsp; &nbsp; 
&nbsp; &nbsp; 
return retval;<br>&nbsp; &nbsp; 
&nbsp; &nbsp; 
}<br>&nbsp; &nbsp; 
};<br>} }<br>&nbsp; &nbsp; 
<br>//Now lets see if the CPoint works with the library functions<br>int main() {<br>&nbsp; &nbsp; 
test_point&lt;CPoint&gt;(); //yay! All your testing is done for you.<br>&nbsp; &nbsp; 
return 0;<br>}<br>&nbsp; &nbsp; 
<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; 
&nbsp;</font></p>


<table class="docinfo" id="table1" frame="void" rules="none">
	<colgroup>
		<col class="docinfo-name"><col class="docinfo-content">
	</colgroup>
	<tbody valign="top">
		<tr>
			<th class="docinfo-name">Copyright:</th>
			<td>Copyright © Intel Corporation 2008-2010.</td>
		</tr>
		<tr class="field">
			<th class="docinfo-name">License:</th>
			<td class="field-body">Distributed under the Boost Software License, 
			Version 1.0. (See accompanying file <tt class="literal">
			<span class="pre">LICENSE_1_0.txt</span></tt> or copy at
			<a class="reference" target="_top" href="http://www.boost.org/LICENSE_1_0.txt">
			http://www.boost.org/LICENSE_1_0.txt</a>)</td>
		</tr>
</tbody></table>

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