// Boost.Geometry (aka GGL, Generic Geometry Library)
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// Copyright (c) 2007-2012 Barend Gehrels, Amsterdam, the Netherlands.
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// This file was modified by Oracle on 2017.
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// Modifications copyright (c) 2017 Oracle and/or its affiliates.
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// Contributed and/or modified by Adam Wulkiewicz, on behalf of Oracle
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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_ALGORITHMS_DETAIL_OVERLAY_GET_RELATIVE_ORDER_HPP
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#define BOOST_GEOMETRY_ALGORITHMS_DETAIL_OVERLAY_GET_RELATIVE_ORDER_HPP
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#include <boost/geometry/strategies/intersection_strategies.hpp>
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namespace boost { namespace geometry
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{
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#ifndef DOXYGEN_NO_DETAIL
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namespace detail { namespace overlay
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{
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/*!
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\brief Get relative order
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\details Can indicate which of two segments R and S,
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both crossing a common segment P, comes first.
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If the two segments cross P very close (e.g. in a spike),
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the distance between the intersection points can be zero,
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but we still need to know which comes first.
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Therefore, it is useful that using sides we are able to discover this.
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*/
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struct get_relative_order
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{
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template <typename Point, typename SideStrategy>
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static inline int value_via_product(Point const& ti, Point const& tj,
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Point const& ui, Point const& uj, int factor,
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SideStrategy const& strategy)
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{
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int const side_ti_u = strategy.apply(ti, tj, ui);
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int const side_tj_u = strategy.apply(ti, tj, uj);
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#ifdef BOOST_GEOMETRY_DEBUG_RELATIVE_ORDER
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std::cout << (factor == 1 ? " r//s " : " s//r ")
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<< side_ti_u << " / " << side_tj_u;
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#endif
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return side_ti_u * side_tj_u >= 0
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? factor * (side_ti_u != 0 ? side_ti_u : side_tj_u)
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: 0;
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}
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template <typename Point1, typename SideStrategy>
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static inline int apply(
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Point1 const& pi, Point1 const& pj,
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Point1 const& ri, Point1 const& rj,
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Point1 const& si, Point1 const& sj,
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SideStrategy const& strategy)
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{
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int const side_ri_p = strategy.apply(pi, pj, ri);
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int const side_si_p = strategy.apply(pi, pj, si);
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#ifdef BOOST_GEOMETRY_DEBUG_RELATIVE_ORDER
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int const side_rj_p = strategy::apply(pi, pj, rj);
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int const side_sj_p = strategy::apply(pi, pj, sj);
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std::cout << "r//p: " << side_ri_p << " / " << side_rj_p;
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std::cout << " s//p: " << side_si_p << " / " << side_sj_p;
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#endif
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int value = value_via_product(si, sj, ri, rj, 1, strategy);
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if (value == 0)
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{
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value = value_via_product(ri, rj, si, sj, -1, strategy);
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}
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int const order = side_ri_p * side_ri_p * side_si_p * value;
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#ifdef BOOST_GEOMETRY_DEBUG_RELATIVE_ORDER
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std::cout
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<< " o: " << order
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<< std::endl << std::endl;
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#endif
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return order;
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}
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};
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}} // namespace detail::overlay
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#endif //DOXYGEN_NO_DETAIL
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}} // namespace boost::geometry
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#endif // BOOST_GEOMETRY_ALGORITHMS_DETAIL_OVERLAY_GET_RELATIVE_ORDER_HPP
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