1 // Copyright (c) 2000
2 // Utrecht University (The Netherlands),
3 // ETH Zurich (Switzerland),
4 // INRIA Sophia-Antipolis (France),
5 // Max-Planck-Institute Saarbruecken (Germany),
6 // and Tel-Aviv University (Israel). All rights reserved.
7 //
8 // This file is part of CGAL (www.cgal.org)
9 //
10 // $URL: https://github.com/CGAL/cgal/blob/v5.3/Intersections_2/include/CGAL/Intersections_2/Line_2_Segment_2.h $
11 // $Id: Line_2_Segment_2.h 0779373 2020-03-26T13:31:46+01:00 Sébastien Loriot
12 // SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
13 //
14 //
15 // Author(s) : Geert-Jan Giezeman
16
17
18 #ifndef CGAL_INTERSECTIONS_2_SEGMENT_2_LINE_2_H
19 #define CGAL_INTERSECTIONS_2_SEGMENT_2_LINE_2_H
20
21 #include <CGAL/Line_2.h>
22 #include <CGAL/Segment_2.h>
23 #include <CGAL/kernel_assertions.h>
24 #include <CGAL/number_utils.h>
25 #include <CGAL/Intersections_2/Line_2_Line_2.h>
26 #include <CGAL/Intersection_traits_2.h>
27
28 namespace CGAL {
29
30 namespace Intersections {
31
32 namespace internal {
33
34 template <class K>
35 class Segment_2_Line_2_pair {
36 public:
37 enum Intersection_results {NO_INTERSECTION, POINT, SEGMENT};
Segment_2_Line_2_pair(typename K::Segment_2 const * seg,typename K::Line_2 const * line)38 Segment_2_Line_2_pair(typename K::Segment_2 const *seg,
39 typename K::Line_2 const *line)
40 : _seg(seg), _line(line), _known(false) {}
41
42 Intersection_results intersection_type() const;
43
44 typename K::Point_2 intersection_point() const;
45 typename K::Segment_2 intersection_segment() const;
46 protected:
47 typename K::Segment_2 const*_seg;
48 typename K::Line_2 const * _line;
49 mutable bool _known;
50 mutable Intersection_results _result;
51 mutable typename K::Point_2 _intersection_point;
52 };
53
54 template <class K>
do_intersect(const typename K::Segment_2 & p1,const typename K::Line_2 & p2,const K &)55 inline bool do_intersect(
56 const typename K::Segment_2 &p1,
57 const typename K::Line_2 &p2,
58 const K&)
59 {
60 typedef Segment_2_Line_2_pair<K> pair_t;
61 pair_t pair(&p1, &p2);
62 return pair.intersection_type() != pair_t::NO_INTERSECTION;
63 }
64
65 template <class K>
66 typename CGAL::Intersection_traits
67 <K, typename K::Segment_2, typename K::Line_2>::result_type
intersection(const typename K::Segment_2 & seg,const typename K::Line_2 & line,const K &)68 intersection(const typename K::Segment_2 &seg,
69 const typename K::Line_2 &line,
70 const K&)
71 {
72 typedef Segment_2_Line_2_pair<K> is_t;
73
74 is_t ispair(&seg, &line);
75 switch (ispair.intersection_type()) {
76 case is_t::NO_INTERSECTION:
77 default:
78 return intersection_return<typename K::Intersect_2, typename K::Line_2, typename K::Segment_2>();
79 case is_t::POINT:
80 return intersection_return<typename K::Intersect_2, typename K::Line_2, typename K::Segment_2>(ispair.intersection_point());
81 case is_t::SEGMENT:
82 return intersection_return<typename K::Intersect_2, typename K::Line_2, typename K::Segment_2>(seg);
83 }
84 }
85
86 template <class K>
87 typename CGAL::Intersection_traits
88 <K, typename K::Line_2, typename K::Segment_2>::result_type
intersection(const typename K::Line_2 & line,const typename K::Segment_2 & seg,const K & k)89 intersection(const typename K::Line_2 &line,
90 const typename K::Segment_2 &seg,
91 const K& k)
92 {
93 return internal::intersection(seg, line, k);
94 }
95
96
97 template <class K>
do_intersect(const typename K::Line_2 & line,const typename K::Segment_2 & seg,const K & k)98 inline bool do_intersect(
99 const typename K::Line_2 &line,
100 const typename K::Segment_2 &seg,
101 const K& k)
102 {
103 return internal::do_intersect(seg, line, k);
104 }
105
106
107 template <class K>
108 typename Segment_2_Line_2_pair<K>::Intersection_results
intersection_type()109 Segment_2_Line_2_pair<K>::intersection_type() const
110 {
111 if (_known)
112 return _result;
113 // The non const this pointer is used to cast away const.
114 _known = true;
115 const typename K::Line_2 &l1 = _seg->supporting_line();
116 Line_2_Line_2_pair<K> linepair(&l1, _line);
117 switch ( linepair.intersection_type()) {
118 case Line_2_Line_2_pair<K>::NO_INTERSECTION:
119 _result = NO_INTERSECTION;
120 break;
121 case Line_2_Line_2_pair<K>::POINT:
122 _intersection_point = linepair.intersection_point();
123 _result = (_seg->collinear_has_on(_intersection_point) )
124 ? POINT : NO_INTERSECTION;
125 break;
126 case Line_2_Line_2_pair<K>::LINE:
127 _result = SEGMENT;
128 break;
129 default:
130 CGAL_assume(false);
131 }
132 return _result;
133 }
134
135 template <class K>
136 typename K::Point_2
intersection_point()137 Segment_2_Line_2_pair<K>::intersection_point() const
138 {
139 if (!_known)
140 intersection_type();
141 CGAL_kernel_assertion(_result == POINT);
142 return _intersection_point;
143 }
144
145 template <class K>
146 typename K::Segment_2
intersection_segment()147 Segment_2_Line_2_pair<K>::intersection_segment() const
148 {
149 if (!_known)
150 intersection_type();
151 CGAL_kernel_assertion(_result == SEGMENT);
152 return *_seg;
153 }
154
155 } // namespace internal
156 } // namespace Intersections
157
158 CGAL_INTERSECTION_FUNCTION(Segment_2, Line_2, 2)
159 CGAL_DO_INTERSECT_FUNCTION(Segment_2, Line_2, 2)
160
161
162 } //namespace CGAL
163
164 #endif
165