1 // Boost.Geometry (aka GGL, Generic Geometry Library)
2 // QuickBook Example
3
4 // Copyright (c) 2020 Digvijay Janartha, Hamirpur, India.
5
6 // Use, modification and distribution is subject to the Boost Software License,
7 // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
8 // http://www.boost.org/LICENSE_1_0.txt)
9
10 //[touches_one_geometry
11 //` Checks if a geometry has at least one touching point (self-tangency)
12
13 #include <iostream>
14
15 #include <boost/geometry.hpp>
16 #include <boost/geometry/geometries/point_xy.hpp>
17 #include <boost/geometry/geometries/polygon.hpp>
18
19 namespace bg = boost::geometry; /*< Convenient namespace alias >*/
20
main()21 int main()
22 {
23 // Checks if the geometry has self-tangency.
24 bg::model::polygon<bg::model::d2::point_xy<double> > poly1;
25 bg::read_wkt("POLYGON((0 0,0 3,2 3,2 2,1 2,1 1,2 1,2 2,3 2,3 0,0 0))", poly1);
26 bool check_touches = bg::touches(poly1);
27 if (check_touches) {
28 std::cout << "Touches: Yes" << std::endl;
29 } else {
30 std::cout << "Touches: No" << std::endl;
31 }
32
33 bg::model::polygon<bg::model::d2::point_xy<double> > poly2;
34 bg::read_wkt("POLYGON((0 0,0 4,4 4,4 0,2 3,0 0))", poly2);
35 check_touches = bg::touches(poly2);
36 if (check_touches) {
37 std::cout << "Touches: Yes" << std::endl;
38 } else {
39 std::cout << "Touches: No" << std::endl;
40 }
41
42 return 0;
43 }
44
45 //]
46
47
48 //[touches_one_geometry_output
49 /*`
50 Output:
51 [pre
52 Touches: Yes
53
54 [$img/algorithms/touches_one_geometry.png]
55
56 Touches: No
57 ]
58 */
59 //]
60
