// Boost.Geometry
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// Copyright (c) 2017-2018 Oracle and/or its affiliates.
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// Contributed and/or modified by Vissarion Fysikopoulos, on behalf of Oracle
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// Contributed and/or modified by Adam Wulkiewicz, on behalf of Oracle
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// Use, modification and distribution is subject to the Boost Software License,
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// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_GEOMETRY_FORMULAS_MERIDIAN_SEGMENT_HPP
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#define BOOST_GEOMETRY_FORMULAS_MERIDIAN_SEGMENT_HPP
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#include <boost/math/constants/constants.hpp>
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#include <boost/geometry/core/radius.hpp>
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#include <boost/geometry/util/condition.hpp>
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#include <boost/geometry/util/math.hpp>
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#include <boost/geometry/util/normalize_spheroidal_coordinates.hpp>
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namespace boost { namespace geometry { namespace formula
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{
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/*!
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\brief Test if a segment is meridian or not.
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*/
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class meridian_segment
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{
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public :
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enum SegmentType {NonMeridian, MeridianCrossingPole, MeridianNotCrossingPole};
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template <typename T>
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static inline SegmentType is_meridian(T lon1, T lat1, T lon2, T lat2)
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{
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SegmentType res = NonMeridian;
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T diff = geometry::math::longitude_distance_signed<geometry::radian>(lon1, lon2);
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if ( meridian_not_crossing_pole(lat1, lat2, diff) )
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{
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res = MeridianNotCrossingPole;
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}
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else if ( meridian_crossing_pole(diff) )
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{
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res = MeridianCrossingPole;
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}
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return res;
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}
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template <typename T>
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static bool meridian_not_crossing_pole(T lat1, T lat2, T diff)
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{
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T half_pi = math::half_pi<T>();
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return math::equals(diff, T(0)) ||
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(math::equals(lat2, half_pi) && math::equals(lat1, -half_pi));
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}
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template <typename T>
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static bool meridian_crossing_pole(T diff)
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{
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return math::equals(math::abs(diff), math::pi<T>());
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}
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};
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}}} // namespace boost::geometry::formula
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#endif //BOOST_GEOMETRY_FORMULAS_MERIDIAN_SEGMENT_HPP
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