Chris@16: // Boost.Geometry (aka GGL, Generic Geometry Library)
Chris@16: 
Chris@16: // Copyright (c) 2007-2012 Barend Gehrels, Amsterdam, the Netherlands.
Chris@16: 
Chris@16: // Use, modification and distribution is subject to the Boost Software License,
Chris@16: // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: #ifndef BOOST_GEOMETRY_STRATEGIES_SPHERICAL_COMPARE_SPHERICAL_HPP
Chris@16: #define BOOST_GEOMETRY_STRATEGIES_SPHERICAL_COMPARE_SPHERICAL_HPP
Chris@16: 
Chris@16: #include <boost/math/constants/constants.hpp>
Chris@16: 
Chris@16: #include <boost/geometry/core/cs.hpp>
Chris@16: #include <boost/geometry/core/tags.hpp>
Chris@16: #include <boost/geometry/strategies/compare.hpp>
Chris@16: #include <boost/geometry/util/math.hpp>
Chris@16: 
Chris@16: 
Chris@16: namespace boost { namespace geometry
Chris@16: {
Chris@16: 
Chris@16: 
Chris@16: namespace strategy { namespace compare
Chris@16: {
Chris@16: 
Chris@16: 
Chris@16: #ifndef DOXYGEN_NO_DETAIL
Chris@16: namespace detail
Chris@16: {
Chris@16: 
Chris@16: template <typename Units>
Chris@16: struct shift
Chris@16: {
Chris@16: };
Chris@16: 
Chris@16: template <>
Chris@16: struct shift<degree>
Chris@16: {
Chris@16:     static inline double full() { return 360.0; }
Chris@16:     static inline double half() { return 180.0; }
Chris@16: };
Chris@16: 
Chris@16: template <>
Chris@16: struct shift<radian>
Chris@16: {
Chris@16:     static inline double full() { return 2.0 * boost::math::constants::pi<double>(); }
Chris@16:     static inline double half() { return boost::math::constants::pi<double>(); }
Chris@16: };
Chris@16: 
Chris@16: } // namespace detail
Chris@16: #endif
Chris@16: 
Chris@16: /*!
Chris@16: \brief Compare (in one direction) strategy for spherical coordinates
Chris@16: \ingroup strategies
Chris@16: \tparam Point point-type
Chris@16: \tparam Dimension dimension
Chris@16: */
Chris@16: template <typename CoordinateType, typename Units, typename Compare>
Chris@16: struct circular_comparator
Chris@16: {
Chris@16:     static inline CoordinateType put_in_range(CoordinateType const& c,
Chris@16:             double min_border, double max_border)
Chris@16:     {
Chris@16:         CoordinateType value = c;
Chris@16:         while (value < min_border)
Chris@16:         {
Chris@16:             value += detail::shift<Units>::full();
Chris@16:         }
Chris@16:         while (value > max_border)
Chris@16:         {
Chris@16:             value -= detail::shift<Units>::full();
Chris@16:         }
Chris@16:         return value;
Chris@16:     }
Chris@16: 
Chris@16:     inline bool operator()(CoordinateType const& c1, CoordinateType const& c2)  const
Chris@16:     {
Chris@16:         Compare compare;
Chris@16: 
Chris@16:         // Check situation that one of them is e.g. std::numeric_limits.
Chris@16:         static const double full = detail::shift<Units>::full();
Chris@16:         double mx = 10.0 * full;
Chris@16:         if (c1 < -mx || c1 > mx || c2 < -mx || c2 > mx)
Chris@16:         {
Chris@16:             // do normal comparison, using circular is not useful
Chris@16:             return compare(c1, c2);
Chris@16:         }
Chris@16: 
Chris@16:         static const double half = full / 2.0;
Chris@16:         CoordinateType v1 = put_in_range(c1, -half, half);
Chris@16:         CoordinateType v2 = put_in_range(c2, -half, half);
Chris@16: 
Chris@16:         // Two coordinates on a circle are
Chris@16:         // at max <= half a circle away from each other.
Chris@16:         // So if it is more, shift origin.
Chris@16:         CoordinateType diff = geometry::math::abs(v1 - v2);
Chris@16:         if (diff > half)
Chris@16:         {
Chris@16:             v1 = put_in_range(v1, 0, full);
Chris@16:             v2 = put_in_range(v2, 0, full);
Chris@16:         }
Chris@16: 
Chris@16:         return compare(v1, v2);
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: }} // namespace strategy::compare
Chris@16: 
Chris@16: #ifndef DOXYGEN_NO_STRATEGY_SPECIALIZATIONS
Chris@16: 
Chris@16: // Specialize for the longitude (dim 0)
Chris@16: template
Chris@16: <
Chris@16:     typename Point,
Chris@16:     template<typename> class CoordinateSystem,
Chris@16:     typename Units
Chris@16: >
Chris@16: struct strategy_compare<spherical_polar_tag, 1, Point, CoordinateSystem<Units>, 0>
Chris@16: {
Chris@16:     typedef typename coordinate_type<Point>::type coordinate_type;
Chris@16:     typedef strategy::compare::circular_comparator
Chris@16:         <
Chris@16:             coordinate_type,
Chris@16:             Units,
Chris@16:             std::less<coordinate_type>
Chris@16:         > type;
Chris@16: };
Chris@16: 
Chris@16: template
Chris@16: <
Chris@16:     typename Point,
Chris@16:     template<typename> class CoordinateSystem,
Chris@16:     typename Units
Chris@16: >
Chris@16: struct strategy_compare<spherical_polar_tag, -1, Point, CoordinateSystem<Units>, 0>
Chris@16: {
Chris@16:     typedef typename coordinate_type<Point>::type coordinate_type;
Chris@16:     typedef strategy::compare::circular_comparator
Chris@16:         <
Chris@16:             coordinate_type,
Chris@16:             Units,
Chris@16:             std::greater<coordinate_type>
Chris@16:         > type;
Chris@16: };
Chris@16: 
Chris@16: #endif // DOXYGEN_NO_STRATEGY_SPECIALIZATIONS
Chris@16: 
Chris@16: }} // namespace boost::geometry
Chris@16: 
Chris@16: #endif // BOOST_GEOMETRY_STRATEGIES_SPHERICAL_COMPARE_SPHERICAL_HPP