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+// Boost.Geometry (aka GGL, Generic Geometry Library)
+
+// Copyright (c) 2007-2012 Barend Gehrels, Amsterdam, the Netherlands.
+// Copyright (c) 2008-2012 Bruno Lalande, Paris, France.
+// Copyright (c) 2009-2012 Mateusz Loskot, London, UK.
+// Copyright (c) 2017 Adam Wulkiewicz, Lodz, Poland.
+
+// This file was modified by Oracle on 2016, 2017.
+// Modifications copyright (c) 2016-2017, Oracle and/or its affiliates.
+
+// Contributed and/or modified by Adam Wulkiewicz, on behalf of Oracle
+
+// Parts of Boost.Geometry are redesigned from Geodan's Geographic Library
+// (geolib/GGL), copyright (c) 1995-2010 Geodan, Amsterdam, the Netherlands.
+
+// Use, modification and distribution is subject to the Boost Software License,
+// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_GEOMETRY_STRATEGIES_CARTESIAN_AREA_HPP
+#define BOOST_GEOMETRY_STRATEGIES_CARTESIAN_AREA_HPP
+
+
+#include <boost/mpl/if.hpp>
+
+//#include <boost/geometry/arithmetic/determinant.hpp>
+#include <boost/geometry/core/coordinate_type.hpp>
+#include <boost/geometry/core/coordinate_dimension.hpp>
+#include <boost/geometry/strategies/area.hpp>
+#include <boost/geometry/util/select_most_precise.hpp>
+
+
+namespace boost { namespace geometry
+{
+
+namespace strategy { namespace area
+{
+
+/*!
+\brief Cartesian area calculation
+\ingroup strategies
+\details Calculates cartesian area using the trapezoidal rule
+\tparam CalculationType \tparam_calculation
+
+\qbk{
+[heading See also]
+[link geometry.reference.algorithms.area.area_2_with_strategy area (with strategy)]
+}
+
+*/
+template
+<
+ typename CalculationType = void
+>
+class cartesian
+{
+public :
+ template <typename Geometry>
+ struct result_type
+ : strategy::area::detail::result_type
+ <
+ Geometry,
+ CalculationType
+ >
+ {};
+
+ template <typename Geometry>
+ class state
+ {
+ friend class cartesian;
+
+ typedef typename result_type<Geometry>::type return_type;
+
+ public:
+ inline state()
+ : sum(0)
+ {
+ // Strategy supports only 2D areas
+ assert_dimension<Geometry, 2>();
+ }
+
+ private:
+ inline return_type area() const
+ {
+ return_type const two = 2;
+ return sum / two;
+ }
+
+ return_type sum;
+ };
+
+ template <typename PointOfSegment, typename Geometry>
+ static inline void apply(PointOfSegment const& p1,
+ PointOfSegment const& p2,
+ state<Geometry>& st)
+ {
+ typedef typename state<Geometry>::return_type return_type;
+
+ // Below formulas are equivalent, however the two lower ones
+ // suffer less from accuracy loss for great values of coordinates.
+ // See: https://svn.boost.org/trac/boost/ticket/11928
+
+ // SUM += x2 * y1 - x1 * y2;
+ // state.sum += detail::determinant<return_type>(p2, p1);
+
+ // SUM += (x2 - x1) * (y2 + y1)
+ //state.sum += (return_type(get<0>(p2)) - return_type(get<0>(p1)))
+ // * (return_type(get<1>(p2)) + return_type(get<1>(p1)));
+
+ // SUM += (x1 + x2) * (y1 - y2)
+ st.sum += (return_type(get<0>(p1)) + return_type(get<0>(p2)))
+ * (return_type(get<1>(p1)) - return_type(get<1>(p2)));
+ }
+
+ template <typename Geometry>
+ static inline typename result_type<Geometry>::type
+ result(state<Geometry>& st)
+ {
+ return st.area();
+ }
+
+};
+
+#ifndef DOXYGEN_NO_STRATEGY_SPECIALIZATIONS
+
+namespace services
+{
+ template <>
+ struct default_strategy<cartesian_tag>
+ {
+ typedef strategy::area::cartesian<> type;
+ };
+
+} // namespace services
+
+#endif // DOXYGEN_NO_STRATEGY_SPECIALIZATIONS
+
+
+}} // namespace strategy::area
+
+
+
+}} // namespace boost::geometry
+
+
+#endif // BOOST_GEOMETRY_STRATEGIES_CARTESIAN_AREA_HPP