173 lines
4.1 KiB
C++
173 lines
4.1 KiB
C++
// Boost.Geometry (aka GGL, Generic Geometry Library)
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// Copyright (c) 2007-2012 Barend Gehrels, Amsterdam, the Netherlands.
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// Copyright (c) 2008-2012 Bruno Lalande, Paris, France.
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// Copyright (c) 2009-2012 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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