316 lines
9.7 KiB
C++
316 lines
9.7 KiB
C++
// Boost.Geometry (aka GGL, Generic Geometry Library)
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// Copyright (c) 2008-2011 Bruno Lalande, Paris, France.
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// Copyright (c) 2008-2011 Barend Gehrels, Amsterdam, the Netherlands.
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// Copyright (c) 2009-2011 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_CARTESIAN_DISTANCE_PROJECTED_POINT_HPP
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#define BOOST_GEOMETRY_STRATEGIES_CARTESIAN_DISTANCE_PROJECTED_POINT_HPP
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#include <boost/concept_check.hpp>
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#include <boost/mpl/if.hpp>
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#include <boost/type_traits.hpp>
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#include <boost/geometry/core/access.hpp>
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#include <boost/geometry/core/point_type.hpp>
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#include <boost/geometry/algorithms/convert.hpp>
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#include <boost/geometry/arithmetic/arithmetic.hpp>
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#include <boost/geometry/arithmetic/dot_product.hpp>
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#include <boost/geometry/strategies/tags.hpp>
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#include <boost/geometry/strategies/distance.hpp>
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#include <boost/geometry/strategies/default_distance_result.hpp>
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#include <boost/geometry/strategies/cartesian/distance_pythagoras.hpp>
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#include <boost/geometry/util/select_coordinate_type.hpp>
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// Helper geometry (projected point on line)
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#include <boost/geometry/geometries/point.hpp>
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namespace boost { namespace geometry
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{
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namespace strategy { namespace distance
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{
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/*!
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\brief Strategy for distance point to segment
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\ingroup strategies
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\details Calculates distance using projected-point method, and (optionally) Pythagoras
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\author Adapted from: http://geometryalgorithms.com/Archive/algorithm_0102/algorithm_0102.htm
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\tparam Point \tparam_point
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\tparam PointOfSegment \tparam_segment_point
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\tparam CalculationType \tparam_calculation
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\tparam Strategy underlying point-point distance strategy
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\par Concepts for Strategy:
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- cartesian_distance operator(Point,Point)
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\note If the Strategy is a "comparable::pythagoras", this strategy
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automatically is a comparable projected_point strategy (so without sqrt)
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\qbk{
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[heading See also]
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[link geometry.reference.algorithms.distance.distance_3_with_strategy distance (with strategy)]
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}
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*/
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template
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<
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typename Point,
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typename PointOfSegment = Point,
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typename CalculationType = void,
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typename Strategy = pythagoras<Point, PointOfSegment, CalculationType>
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>
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class projected_point
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{
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public :
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typedef typename strategy::distance::services::return_type<Strategy>::type calculation_type;
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private :
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// The three typedefs below are necessary to calculate distances
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// from segments defined in integer coordinates.
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// Integer coordinates can still result in FP distances.
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// There is a division, which must be represented in FP.
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// So promote.
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typedef typename promote_floating_point<calculation_type>::type fp_type;
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// A projected point of points in Integer coordinates must be able to be
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// represented in FP.
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typedef model::point
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<
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fp_type,
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dimension<PointOfSegment>::value,
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typename coordinate_system<PointOfSegment>::type
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> fp_point_type;
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// For convenience
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typedef fp_point_type fp_vector_type;
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// We have to use a strategy using FP coordinates (fp-type) which is
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// not always the same as Strategy (defined as point_strategy_type)
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// So we create a "similar" one
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typedef typename strategy::distance::services::similar_type
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<
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Strategy,
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Point,
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fp_point_type
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>::type fp_strategy_type;
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public :
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inline calculation_type apply(Point const& p,
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PointOfSegment const& p1, PointOfSegment const& p2) const
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{
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assert_dimension_equal<Point, PointOfSegment>();
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/*
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Algorithm [p1: (x1,y1), p2: (x2,y2), p: (px,py)]
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VECTOR v(x2 - x1, y2 - y1)
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VECTOR w(px - x1, py - y1)
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c1 = w . v
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c2 = v . v
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b = c1 / c2
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RETURN POINT(x1 + b * vx, y1 + b * vy)
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*/
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// v is multiplied below with a (possibly) FP-value, so should be in FP
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// For consistency we define w also in FP
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fp_vector_type v, w;
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geometry::convert(p2, v);
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geometry::convert(p, w);
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subtract_point(v, p1);
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subtract_point(w, p1);
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Strategy strategy;
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boost::ignore_unused_variable_warning(strategy);
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calculation_type const zero = calculation_type();
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fp_type const c1 = dot_product(w, v);
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if (c1 <= zero)
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{
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return strategy.apply(p, p1);
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}
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fp_type const c2 = dot_product(v, v);
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if (c2 <= c1)
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{
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return strategy.apply(p, p2);
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}
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// See above, c1 > 0 AND c2 > c1 so: c2 != 0
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fp_type const b = c1 / c2;
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fp_strategy_type fp_strategy
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= strategy::distance::services::get_similar
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<
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Strategy, Point, fp_point_type
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>::apply(strategy);
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fp_point_type projected;
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geometry::convert(p1, projected);
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multiply_value(v, b);
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add_point(projected, v);
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//std::cout << "distance " << dsv(p) << " .. " << dsv(projected) << std::endl;
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return fp_strategy.apply(p, projected);
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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 <typename Point, typename PointOfSegment, typename CalculationType, typename Strategy>
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struct tag<projected_point<Point, PointOfSegment, CalculationType, Strategy> >
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{
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typedef strategy_tag_distance_point_segment type;
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};
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template <typename Point, typename PointOfSegment, typename CalculationType, typename Strategy>
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struct return_type<projected_point<Point, PointOfSegment, CalculationType, Strategy> >
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{
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typedef typename projected_point<Point, PointOfSegment, CalculationType, Strategy>::calculation_type type;
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};
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template <typename Point, typename PointOfSegment, typename CalculationType, typename Strategy>
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struct strategy_point_point<projected_point<Point, PointOfSegment, CalculationType, Strategy> >
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{
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typedef Strategy type;
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};
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template
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<
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typename Point,
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typename PointOfSegment,
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typename CalculationType,
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typename Strategy,
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typename P1,
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typename P2
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>
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struct similar_type<projected_point<Point, PointOfSegment, CalculationType, Strategy>, P1, P2>
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{
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typedef projected_point<P1, P2, CalculationType, Strategy> type;
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};
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template
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<
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typename Point,
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typename PointOfSegment,
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typename CalculationType,
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typename Strategy,
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typename P1,
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typename P2
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>
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struct get_similar<projected_point<Point, PointOfSegment, CalculationType, Strategy>, P1, P2>
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{
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static inline typename similar_type
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<
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projected_point<Point, PointOfSegment, CalculationType, Strategy>, P1, P2
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>::type apply(projected_point<Point, PointOfSegment, CalculationType, Strategy> const& )
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{
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return projected_point<P1, P2, CalculationType, Strategy>();
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}
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};
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template <typename Point, typename PointOfSegment, typename CalculationType, typename Strategy>
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struct comparable_type<projected_point<Point, PointOfSegment, CalculationType, Strategy> >
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{
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// Define a projected_point strategy with its underlying point-point-strategy
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// being comparable
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typedef projected_point
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<
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Point,
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PointOfSegment,
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CalculationType,
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typename comparable_type<Strategy>::type
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> type;
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};
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template <typename Point, typename PointOfSegment, typename CalculationType, typename Strategy>
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struct get_comparable<projected_point<Point, PointOfSegment, CalculationType, Strategy> >
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{
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typedef typename comparable_type
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<
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projected_point<Point, PointOfSegment, CalculationType, Strategy>
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>::type comparable_type;
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public :
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static inline comparable_type apply(projected_point<Point, PointOfSegment, CalculationType, Strategy> const& )
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{
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return comparable_type();
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}
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};
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template <typename Point, typename PointOfSegment, typename CalculationType, typename Strategy>
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struct result_from_distance<projected_point<Point, PointOfSegment, CalculationType, Strategy> >
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{
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private :
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typedef typename return_type<projected_point<Point, PointOfSegment, CalculationType, Strategy> >::type return_type;
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public :
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template <typename T>
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static inline return_type apply(projected_point<Point, PointOfSegment, CalculationType, Strategy> const& , T const& value)
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{
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Strategy s;
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return result_from_distance<Strategy>::apply(s, value);
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}
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};
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// Get default-strategy for point-segment distance calculation
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// while still have the possibility to specify point-point distance strategy (PPS)
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// It is used in algorithms/distance.hpp where users specify PPS for distance
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// of point-to-segment or point-to-linestring.
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// Convenient for geographic coordinate systems especially.
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template <typename Point, typename PointOfSegment, typename Strategy>
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struct default_strategy<segment_tag, Point, PointOfSegment, cartesian_tag, cartesian_tag, Strategy>
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{
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typedef strategy::distance::projected_point
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<
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Point,
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PointOfSegment,
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void,
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typename boost::mpl::if_
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<
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boost::is_void<Strategy>,
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typename default_strategy
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<
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point_tag, Point, PointOfSegment,
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cartesian_tag, cartesian_tag
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>::type,
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Strategy
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>::type
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> 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::distance
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}} // namespace boost::geometry
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#endif // BOOST_GEOMETRY_STRATEGIES_CARTESIAN_DISTANCE_PROJECTED_POINT_HPP
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