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172 lines
4.0 KiB
172 lines
4.0 KiB
// Boost.Geometry (aka GGL, Generic Geometry Library) |
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// Copyright (c) 2007-2011 Barend Gehrels, Amsterdam, the Netherlands. |
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// Copyright (c) 2008-2011 Bruno Lalande, Paris, France. |
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// Copyright (c) 2009-2011 Mateusz Loskot, London, UK. |
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// Parts of Boost.Geometry are redesigned from Geodan's Geographic Library |
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// (geolib/GGL), copyright (c) 1995-2010 Geodan, Amsterdam, the Netherlands. |
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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_STRATEGIES_COMPARE_HPP |
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#define BOOST_GEOMETRY_STRATEGIES_COMPARE_HPP |
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#include <cstddef> |
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#include <functional> |
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#include <boost/mpl/if.hpp> |
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#include <boost/geometry/core/cs.hpp> |
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#include <boost/geometry/core/coordinate_type.hpp> |
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#include <boost/geometry/strategies/tags.hpp> |
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namespace boost { namespace geometry |
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{ |
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/*! |
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\brief Traits class binding a comparing strategy to a coordinate system |
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\ingroup util |
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\tparam Tag tag of coordinate system of point-type |
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\tparam Direction direction to compare on: 1 for less (-> ascending order) |
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and -1 for greater (-> descending order) |
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\tparam Point point-type |
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\tparam CoordinateSystem coordinate sytem of point |
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\tparam Dimension: the dimension to compare on |
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*/ |
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template |
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< |
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typename Tag, |
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int Direction, |
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typename Point, |
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typename CoordinateSystem, |
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std::size_t Dimension |
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> |
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struct strategy_compare |
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{ |
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typedef strategy::not_implemented type; |
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}; |
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#ifndef DOXYGEN_NO_STRATEGY_SPECIALIZATIONS |
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// For compare we add defaults specializations, |
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// because they defaultly redirect to std::less / greater / equal_to |
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template |
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< |
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typename Tag, |
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typename Point, |
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typename CoordinateSystem, |
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std::size_t Dimension |
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> |
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struct strategy_compare<Tag, 1, Point, CoordinateSystem, Dimension> |
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{ |
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typedef std::less<typename coordinate_type<Point>::type> type; |
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}; |
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template |
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< |
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typename Tag, |
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typename Point, |
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typename CoordinateSystem, |
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std::size_t Dimension |
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> |
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struct strategy_compare<Tag, -1, Point, CoordinateSystem, Dimension> |
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{ |
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typedef std::greater<typename coordinate_type<Point>::type> type; |
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}; |
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template |
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< |
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typename Tag, |
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typename Point, |
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typename CoordinateSystem, |
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std::size_t Dimension |
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> |
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struct strategy_compare<Tag, 0, Point, CoordinateSystem, Dimension> |
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{ |
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typedef std::equal_to<typename coordinate_type<Point>::type> type; |
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}; |
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#endif |
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namespace strategy { namespace compare |
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{ |
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/*! |
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\brief Default strategy, indicates the default strategy for comparisons |
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\details The default strategy for comparisons defer in most cases |
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to std::less (for ascending) and std::greater (for descending). |
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However, if a spherical coordinate system is used, and comparison |
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is done on longitude, it will take another strategy handling circular |
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*/ |
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struct default_strategy {}; |
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#ifndef DOXYGEN_NO_DETAIL |
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namespace detail |
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{ |
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template <typename Type> |
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struct is_default : boost::false_type |
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{}; |
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template <> |
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struct is_default<default_strategy> : boost::true_type |
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{}; |
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/*! |
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\brief Meta-function to select strategy |
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\details If "default_strategy" is specified, it will take the |
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traits-registered class for the specified coordinate system. |
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If another strategy is explicitly specified, it takes that one. |
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*/ |
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template |
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< |
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typename Strategy, |
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int Direction, |
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typename Point, |
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std::size_t Dimension |
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> |
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struct select_strategy |
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{ |
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typedef typename |
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boost::mpl::if_ |
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< |
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is_default<Strategy>, |
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typename strategy_compare |
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< |
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typename cs_tag<Point>::type, |
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Direction, |
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Point, |
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typename coordinate_system<Point>::type, |
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Dimension |
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>::type, |
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Strategy |
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>::type type; |
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}; |
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} // namespace detail |
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#endif // DOXYGEN_NO_DETAIL |
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}} // namespace strategy::compare |
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}} // namespace boost::geometry |
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#endif // BOOST_GEOMETRY_STRATEGIES_COMPARE_HPP
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