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1 | // Boost.Geometry (aka GGL, Generic Geometry Library) |
2 | // QuickBook Example | |
3 | ||
4 | // Copyright (c) 2011-2012 Barend Gehrels, Amsterdam, the Netherlands. | |
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 | //[for_each_segment_const | |
11 | //` Sample using for_each_segment, using a functor to get the minimum and maximum length of a segment in a linestring | |
12 | ||
13 | #include <iostream> | |
14 | ||
15 | #include <boost/geometry.hpp> | |
16 | #include <boost/geometry/geometries/linestring.hpp> | |
17 | #include <boost/geometry/geometries/point_xy.hpp> | |
18 | ||
19 | #include <boost/assign.hpp> | |
20 | ||
21 | ||
22 | template <typename Segment> | |
23 | struct gather_segment_statistics | |
24 | { | |
25 | // Remember that if coordinates are integer, the length might be floating point | |
26 | // So use "double" for integers. In other cases, use coordinate type | |
27 | typedef typename boost::geometry::select_most_precise | |
28 | < | |
29 | typename boost::geometry::coordinate_type<Segment>::type, | |
30 | double | |
31 | >::type type; | |
32 | ||
33 | type min_length, max_length; | |
34 | ||
35 | // Initialize min and max | |
36 | gather_segment_statistics() | |
37 | : min_length(1e38) | |
38 | , max_length(-1) | |
39 | {} | |
40 | ||
41 | // This operator is called for each segment | |
42 | inline void operator()(Segment const& s) | |
43 | { | |
44 | type length = boost::geometry::length(s); | |
45 | if (length < min_length) min_length = length; | |
46 | if (length > max_length) max_length = length; | |
47 | } | |
48 | }; | |
49 | ||
50 | int main() | |
51 | { | |
52 | // Bring "+=" for a vector into scope | |
53 | using namespace boost::assign; | |
54 | ||
55 | // Define a type | |
56 | typedef boost::geometry::model::d2::point_xy<double> point; | |
57 | ||
58 | // Declare a linestring | |
59 | boost::geometry::model::linestring<point> polyline; | |
60 | ||
61 | // Use Boost.Assign to initialize a linestring | |
62 | polyline += point(0, 0), point(3, 3), point(5, 1), point(6, 2), | |
63 | point(8, 0), point(4, -4), point(1, -1), point(3, 2); | |
64 | ||
65 | ||
66 | // Declare the gathering class... | |
67 | gather_segment_statistics | |
68 | < | |
69 | boost::geometry::model::referring_segment<point> | |
70 | > functor; | |
71 | ||
72 | // ... and use it, the essention. | |
73 | // As also in std::for_each it is a const value, so retrieve it as a return value. | |
74 | functor = boost::geometry::for_each_segment(polyline, functor); | |
75 | ||
76 | // Output the results | |
77 | std::cout | |
78 | << "Min segment length: " << functor.min_length << std::endl | |
79 | << "Max segment length: " << functor.max_length << std::endl; | |
80 | ||
81 | return 0; | |
82 | } | |
83 | ||
84 | //] | |
85 | ||
86 | ||
87 | //[for_each_segment_const_output | |
88 | /*` | |
89 | Output: | |
90 | [pre | |
91 | Min segment length: 1.41421 | |
92 | Max segment length: 5.65685 | |
93 | ] | |
94 | */ | |
95 | //] |