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1 | // Boost.Geometry (aka GGL, Generic Geometry Library) |
2 | ||
3 | // Copyright (c) 2007-2012 Barend Gehrels, Amsterdam, the Netherlands. | |
4 | // Copyright (c) 2008-2012 Bruno Lalande, Paris, France. | |
5 | // Copyright (c) 2009-2012 Mateusz Loskot, London, UK. | |
6 | ||
7 | // Parts of Boost.Geometry are redesigned from Geodan's Geographic Library | |
8 | // (geolib/GGL), copyright (c) 1995-2010 Geodan, Amsterdam, the Netherlands. | |
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 | ||
15 | #ifndef BOOST_GEOMETRY_STRATEGIES_COMPARE_HPP | |
16 | #define BOOST_GEOMETRY_STRATEGIES_COMPARE_HPP | |
17 | ||
18 | #include <cstddef> | |
19 | #include <functional> | |
20 | ||
21 | #include <boost/mpl/if.hpp> | |
22 | ||
23 | #include <boost/geometry/core/cs.hpp> | |
24 | #include <boost/geometry/core/coordinate_type.hpp> | |
25 | ||
26 | #include <boost/geometry/strategies/tags.hpp> | |
27 | ||
28 | ||
29 | namespace boost { namespace geometry | |
30 | { | |
31 | ||
32 | ||
33 | /*! | |
34 | \brief Traits class binding a comparing strategy to a coordinate system | |
35 | \ingroup util | |
36 | \tparam Tag tag of coordinate system of point-type | |
37 | \tparam Direction direction to compare on: 1 for less (-> ascending order) | |
38 | and -1 for greater (-> descending order) | |
39 | \tparam Point point-type | |
40 | \tparam CoordinateSystem coordinate sytem of point | |
41 | \tparam Dimension: the dimension to compare on | |
42 | */ | |
43 | template | |
44 | < | |
45 | typename Tag, | |
46 | int Direction, | |
47 | typename Point, | |
48 | typename CoordinateSystem, | |
49 | std::size_t Dimension | |
50 | > | |
51 | struct strategy_compare | |
52 | { | |
53 | typedef strategy::not_implemented type; | |
54 | }; | |
55 | ||
56 | ||
57 | #ifndef DOXYGEN_NO_STRATEGY_SPECIALIZATIONS | |
58 | ||
59 | // For compare we add defaults specializations, | |
60 | // because they defaultly redirect to std::less / greater / equal_to | |
61 | template | |
62 | < | |
63 | typename Tag, | |
64 | typename Point, | |
65 | typename CoordinateSystem, | |
66 | std::size_t Dimension | |
67 | > | |
68 | struct strategy_compare<Tag, 1, Point, CoordinateSystem, Dimension> | |
69 | { | |
70 | typedef std::less<typename coordinate_type<Point>::type> type; | |
71 | }; | |
72 | ||
73 | ||
74 | template | |
75 | < | |
76 | typename Tag, | |
77 | typename Point, | |
78 | typename CoordinateSystem, | |
79 | std::size_t Dimension | |
80 | > | |
81 | struct strategy_compare<Tag, -1, Point, CoordinateSystem, Dimension> | |
82 | { | |
83 | typedef std::greater<typename coordinate_type<Point>::type> type; | |
84 | }; | |
85 | ||
86 | ||
87 | template | |
88 | < | |
89 | typename Tag, | |
90 | typename Point, | |
91 | typename CoordinateSystem, | |
92 | std::size_t Dimension | |
93 | > | |
94 | struct strategy_compare<Tag, 0, Point, CoordinateSystem, Dimension> | |
95 | { | |
96 | typedef std::equal_to<typename coordinate_type<Point>::type> type; | |
97 | }; | |
98 | ||
99 | ||
100 | #endif | |
101 | ||
102 | ||
103 | namespace strategy { namespace compare | |
104 | { | |
105 | ||
106 | ||
107 | /*! | |
108 | \brief Default strategy, indicates the default strategy for comparisons | |
109 | \details The default strategy for comparisons defer in most cases | |
110 | to std::less (for ascending) and std::greater (for descending). | |
111 | However, if a spherical coordinate system is used, and comparison | |
112 | is done on longitude, it will take another strategy handling circular | |
113 | */ | |
114 | struct default_strategy {}; | |
115 | ||
116 | ||
117 | #ifndef DOXYGEN_NO_DETAIL | |
118 | namespace detail | |
119 | { | |
120 | ||
121 | template <typename Type> | |
122 | struct is_default : boost::false_type | |
123 | {}; | |
124 | ||
125 | ||
126 | template <> | |
127 | struct is_default<default_strategy> : boost::true_type | |
128 | {}; | |
129 | ||
130 | ||
131 | /*! | |
132 | \brief Meta-function to select strategy | |
133 | \details If "default_strategy" is specified, it will take the | |
134 | traits-registered class for the specified coordinate system. | |
135 | If another strategy is explicitly specified, it takes that one. | |
136 | */ | |
137 | template | |
138 | < | |
139 | typename Strategy, | |
140 | int Direction, | |
141 | typename Point, | |
142 | std::size_t Dimension | |
143 | > | |
144 | struct select_strategy | |
145 | { | |
146 | typedef typename | |
147 | boost::mpl::if_ | |
148 | < | |
149 | is_default<Strategy>, | |
150 | typename strategy_compare | |
151 | < | |
152 | typename cs_tag<Point>::type, | |
153 | Direction, | |
154 | Point, | |
155 | typename coordinate_system<Point>::type, | |
156 | Dimension | |
157 | >::type, | |
158 | Strategy | |
159 | >::type type; | |
160 | }; | |
161 | ||
162 | } // namespace detail | |
163 | #endif // DOXYGEN_NO_DETAIL | |
164 | ||
165 | ||
166 | }} // namespace strategy::compare | |
167 | ||
168 | ||
169 | }} // namespace boost::geometry | |
170 | ||
171 | ||
172 | #endif // BOOST_GEOMETRY_STRATEGIES_COMPARE_HPP |