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1 : : /*
2 : : * Copyright 2010 Savarese Software Research Corporation
3 : : *
4 : : * Licensed under the Apache License, Version 2.0 (the "License");
5 : : * you may not use this file except in compliance with the License.
6 : : * You may obtain a copy of the License at
7 : : *
8 : : * https://www.savarese.com/software/ApacheLicense-2.0
9 : : *
10 : : * Unless required by applicable law or agreed to in writing, software
11 : : * distributed under the License is distributed on an "AS IS" BASIS,
12 : : * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 : : * See the License for the specific language governing permissions and
14 : : * limitations under the License.
15 : : */
16 : :
17 : : /**
18 : : * @file
19 : : * This header defines distance functions.
20 : : */
21 : :
22 : : #ifndef __SSRC_SPATIAL_DISTANCE_H
23 : : #define __SSRC_SPATIAL_DISTANCE_H
24 : :
25 : : #include <ssrc/libssrckdtree-packages.h>
26 : :
27 : : #include <tuple>
28 : :
29 : : __BEGIN_NS_SSRC_SPATIAL
30 : :
31 : : /**
32 : : * euclidean_distance is a template class that houses functions for
33 : : * determining distances and distance-related values in a Euclidean
34 : : * space. These functions are static and rely on the enclosing class
35 : : * to enable implementation of partial specializations.
36 : : */
37 : : template<typename Point,
38 : : typename Distance = double,
39 : : const unsigned int i = NS_TR1::tuple_size<Point>::value - 1>
40 : : struct euclidean_distance {
41 : : typedef Distance distance_type;
42 : :
43 : : /**
44 : : * Returns the square of the distance between two points.
45 : : *
46 : : * @param from The first end point.
47 : : * @param to The second end point.
48 : : * @return The square of the distance between from and to.
49 : : */
50 : 6 : static distance_type d2(const Point & from, const Point & to) {
51 : : const distance_type d =
52 : 6 : static_cast<distance_type>(to[i]) - static_cast<distance_type>(from[i]);
53 : :
54 : 6 : return (d*d) + euclidean_distance<Point, distance_type, i-1>::d2(from, to);
55 : : }
56 : : };
57 : :
58 : : template<typename Point, typename Distance>
59 : : struct euclidean_distance<Point, Distance, 0> {
60 : : typedef Distance distance_type;
61 : :
62 : 12 : static distance_type d2(const Point & from, const Point & to) {
63 : : const distance_type d0 =
64 : 12 : static_cast<distance_type>(to[0]) - static_cast<distance_type>(from[0]);
65 : :
66 : 12 : return (d0*d0);
67 : : }
68 : : };
69 : :
70 : : template<typename Point, typename Distance>
71 : : struct euclidean_distance<Point, Distance, 1> {
72 : : typedef Distance distance_type;
73 : :
74 : 1781198 : static distance_type d2(const Point & from, const Point & to) {
75 : : const distance_type d0 =
76 : 1781198 : static_cast<distance_type>(to[0]) - static_cast<distance_type>(from[0]);
77 : : const distance_type d1 =
78 : 1781198 : static_cast<distance_type>(to[1]) - static_cast<distance_type>(from[1]);
79 : :
80 : 1781198 : return (d0*d0) + (d1*d1);
81 : : }
82 : : };
83 : :
84 : : template<typename Point, typename Distance>
85 : : struct euclidean_distance<Point, Distance, 2> {
86 : : typedef Distance distance_type;
87 : :
88 : 15 : static distance_type d2(const Point & from, const Point & to) {
89 : : const distance_type d0 =
90 : 15 : static_cast<distance_type>(to[0]) - static_cast<distance_type>(from[0]);
91 : : const distance_type d1 =
92 : 15 : static_cast<distance_type>(to[1]) - static_cast<distance_type>(from[1]);
93 : : const distance_type d2 =
94 : 15 : static_cast<distance_type>(to[2]) - static_cast<distance_type>(from[2]);
95 : :
96 : 15 : return (d0*d0) + (d1*d1) + (d2*d2);
97 : : }
98 : : };
99 : :
100 : : __END_NS_SSRC_SPATIAL
101 : :
102 : : #endif
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