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1 | // Boost.Geometry (aka GGL, Generic Geometry Library) | |
2 | ||
3 | // Copyright (c) 2015 Barend Gehrels, Amsterdam, the Netherlands. | |
4 | ||
5 | // This file was modified by Oracle on 2015. | |
6 | // Modifications copyright (c) 2015 Oracle and/or its affiliates. | |
7 | ||
8 | // Contributed and/or modified by Menelaos Karavelas, on behalf of Oracle | |
9 | ||
10 | // Use, modification and distribution is subject to the Boost Software License, | |
11 | // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at | |
12 | // http://www.boost.org/LICENSE_1_0.txt) | |
13 | ||
14 | #ifndef BOOST_GEOMETRY_ALGORITHMS_DETAIL_DIRECITON_CODE_HPP | |
15 | #define BOOST_GEOMETRY_ALGORITHMS_DETAIL_DIRECITON_CODE_HPP | |
16 | ||
17 | ||
18 | #include <boost/geometry/core/access.hpp> | |
19 | #include <boost/geometry/util/math.hpp> | |
20 | ||
21 | namespace boost { namespace geometry | |
22 | { | |
23 | ||
24 | #ifndef DOXYGEN_NO_DETAIL | |
25 | namespace detail | |
26 | { | |
27 | ||
28 | template <std::size_t Index, typename Point1, typename Point2> | |
29 | inline int sign_of_difference(Point1 const& point1, Point2 const& point2) | |
30 | { | |
31 | return | |
32 | math::equals(geometry::get<Index>(point1), geometry::get<Index>(point2)) | |
33 | ? | |
34 | 0 | |
35 | : | |
36 | (geometry::get<Index>(point1) > geometry::get<Index>(point2) ? 1 : -1); | |
37 | } | |
38 | ||
39 | ||
40 | // Gives sense of direction for point p, collinear w.r.t. segment (a,b) | |
41 | // Returns -1 if p goes backward w.r.t (a,b), so goes from b in direction of a | |
42 | // Returns 1 if p goes forward, so extends (a,b) | |
43 | // Returns 0 if p is equal with b, or if (a,b) is degenerate | |
44 | // Note that it does not do any collinearity test, that should be done before | |
45 | template <typename Point1, typename Point2> | |
46 | inline int direction_code(Point1 const& segment_a, Point1 const& segment_b, | |
47 | const Point2& p) | |
48 | { | |
49 | // Suppose segment = (4 3,4 4) and p =(4 2) | |
50 | // Then sign_a1 = 1 and sign_p1 = 1 -> goes backward -> return -1 | |
51 | ||
52 | int const sign_a0 = sign_of_difference<0>(segment_b, segment_a); | |
53 | int const sign_a1 = sign_of_difference<1>(segment_b, segment_a); | |
54 | ||
55 | if (sign_a0 == 0 && sign_a1 == 0) | |
56 | { | |
57 | return 0; | |
58 | } | |
59 | ||
60 | int const sign_p0 = sign_of_difference<0>(segment_b, p); | |
61 | int const sign_p1 = sign_of_difference<1>(segment_b, p); | |
62 | ||
63 | if (sign_p0 == 0 && sign_p1 == 0) | |
64 | { | |
65 | return 0; | |
66 | } | |
67 | ||
68 | return sign_a0 == sign_p0 && sign_a1 == sign_p1 ? -1 : 1; | |
69 | } | |
70 | ||
71 | ||
72 | } // namespace detail | |
73 | #endif //DOXYGEN_NO_DETAIL | |
74 | ||
75 | ||
76 | ||
77 | }} // namespace boost::geometry | |
78 | ||
79 | #endif // BOOST_GEOMETRY_ALGORITHMS_DETAIL_DIRECITON_CODE_HPP |