100 lines
2.8 KiB
C++
100 lines
2.8 KiB
C++
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// Boost.Geometry
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// Copyright (c) 2020-2021, Oracle and/or its affiliates.
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// Contributed and/or modified by Vissarion Fysikopoulos, on behalf of Oracle
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// Licensed under the Boost Software License version 1.0.
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// http://www.boost.org/users/license.html
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#ifndef BOOST_GEOMETRY_STRATEGY_CARTESIAN_SIDE_NON_ROBUST_HPP
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#define BOOST_GEOMETRY_STRATEGY_CARTESIAN_SIDE_NON_ROBUST_HPP
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#include <boost/geometry/util/select_most_precise.hpp>
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#include <boost/geometry/util/select_calculation_type.hpp>
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#include <boost/geometry/util/precise_math.hpp>
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#include <boost/geometry/arithmetic/determinant.hpp>
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namespace boost { namespace geometry
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{
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namespace strategy { namespace side
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{
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/*!
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\brief Predicate to check at which side of a segment a point lies:
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left of segment (>0), right of segment (< 0), on segment (0).
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\ingroup strategies
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\tparam CalculationType \tparam_calculation
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\details This predicate determines at which side of a segment a point lies
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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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struct side_non_robust
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{
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public:
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//! \brief Computes double the signed area of the CCW triangle p1, p2, p
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template
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<
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typename P1,
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typename P2,
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typename P
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>
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static inline int apply(P1 const& p1, P2 const& p2, P const& p)
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{
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typedef typename select_calculation_type_alt
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<
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CalculationType,
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P1,
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P2,
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P
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>::type CoordinateType;
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typedef typename select_most_precise
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<
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CoordinateType,
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double
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>::type PromotedType;
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CoordinateType const x = get<0>(p);
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CoordinateType const y = get<1>(p);
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CoordinateType const sx1 = get<0>(p1);
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CoordinateType const sy1 = get<1>(p1);
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CoordinateType const sx2 = get<0>(p2);
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CoordinateType const sy2 = get<1>(p2);
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//non-robust 1
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//the following is 2x slower in some generic cases when compiled with g++
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//(tested versions 9 and 10)
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//
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//auto detleft = (sx1 - x) * (sy2 - y);
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//auto detright = (sy1 - y) * (sx2 - x);
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//return detleft > detright ? 1 : (detleft < detright ? -1 : 0 );
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//non-robust 2
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PromotedType const dx = sx2 - sx1;
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PromotedType const dy = sy2 - sy1;
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PromotedType const dpx = x - sx1;
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PromotedType const dpy = y - sy1;
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PromotedType sv = geometry::detail::determinant<PromotedType>
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(
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dx, dy,
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dpx, dpy
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);
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PromotedType const zero = PromotedType();
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return sv == zero ? 0 : sv > zero ? 1 : -1;
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}
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};
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}} // namespace strategy::side
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}} // namespace boost::geometry
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#endif // BOOST_GEOMETRY_STRATEGY_CARTESIAN_SIDE_NON_ROBUST_HPP
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