145 lines
3.8 KiB
C++
145 lines
3.8 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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// Copyright (c) 2017 Adam Wulkiewicz, Lodz, Poland.
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// This file was modified by Oracle on 2016-2020.
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// Modifications copyright (c) 2016-2020, Oracle and/or its affiliates.
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// Contributed and/or modified by Adam Wulkiewicz, on behalf of Oracle
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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_STRATEGY_CARTESIAN_AREA_HPP
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#define BOOST_GEOMETRY_STRATEGY_CARTESIAN_AREA_HPP
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//#include <boost/geometry/arithmetic/determinant.hpp>
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#include <boost/geometry/core/access.hpp>
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#include <boost/geometry/core/coordinate_type.hpp>
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#include <boost/geometry/core/coordinate_dimension.hpp>
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#include <boost/geometry/strategy/area.hpp>
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#include <boost/geometry/util/select_most_precise.hpp>
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namespace boost { namespace geometry
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{
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namespace strategy { namespace area
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{
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/*!
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\brief Cartesian area calculation
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\ingroup strategies
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\details Calculates cartesian area using the trapezoidal rule
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\tparam CalculationType \tparam_calculation
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\qbk{
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[heading See also]
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[link geometry.reference.algorithms.area.area_2_with_strategy area (with strategy)]
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}
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*/
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template
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<
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typename CalculationType = void
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>
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class cartesian
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{
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public :
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template <typename Geometry>
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struct result_type
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: strategy::area::detail::result_type
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<
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Geometry,
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CalculationType
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>
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{};
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template <typename Geometry>
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class state
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{
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friend class cartesian;
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typedef typename result_type<Geometry>::type return_type;
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public:
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inline state()
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: sum(0)
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{
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// Strategy supports only 2D areas
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assert_dimension<Geometry, 2>();
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}
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private:
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inline return_type area() const
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{
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return_type const two = 2;
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return sum / two;
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}
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return_type sum;
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};
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template <typename PointOfSegment, typename Geometry>
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static inline void apply(PointOfSegment const& p1,
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PointOfSegment const& p2,
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state<Geometry>& st)
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{
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typedef typename state<Geometry>::return_type return_type;
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// Below formulas are equivalent, however the two lower ones
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// suffer less from accuracy loss for great values of coordinates.
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// See: https://svn.boost.org/trac/boost/ticket/11928
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// SUM += x2 * y1 - x1 * y2;
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// state.sum += detail::determinant<return_type>(p2, p1);
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// SUM += (x2 - x1) * (y2 + y1)
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//state.sum += (return_type(get<0>(p2)) - return_type(get<0>(p1)))
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// * (return_type(get<1>(p2)) + return_type(get<1>(p1)));
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// SUM += (x1 + x2) * (y1 - y2)
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st.sum += (return_type(get<0>(p1)) + return_type(get<0>(p2)))
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* (return_type(get<1>(p1)) - return_type(get<1>(p2)));
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}
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template <typename Geometry>
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static inline auto result(state<Geometry>& st)
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{
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return st.area();
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}
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};
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#ifndef DOXYGEN_NO_STRATEGY_SPECIALIZATIONS
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namespace services
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{
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template <>
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struct default_strategy<cartesian_tag>
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{
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typedef strategy::area::cartesian<> type;
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};
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} // namespace services
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#endif // DOXYGEN_NO_STRATEGY_SPECIALIZATIONS
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}} // namespace strategy::area
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}} // namespace boost::geometry
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#endif // BOOST_GEOMETRY_STRATEGY_CARTESIAN_AREA_HPP
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