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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.
// 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_SIDE_BY_TRIANGLE_HPP
#define BOOST_GEOMETRY_STRATEGIES_CARTESIAN_SIDE_BY_TRIANGLE_HPP
#include <boost/mpl/if.hpp>
#include <boost/type_traits.hpp>
#include <boost/geometry/arithmetic/determinant.hpp>
#include <boost/geometry/core/access.hpp>
#include <boost/geometry/util/select_coordinate_type.hpp>
#include <boost/geometry/strategies/side.hpp>
namespace boost { namespace geometry
{
namespace strategy { namespace side
{
/*!
\brief Check at which side of a segment a point lies:
left of segment (> 0), right of segment (< 0), on segment (0)
\ingroup strategies
\tparam CalculationType \tparam_calculation
*/
template <typename CalculationType = void>
class side_by_triangle
{
public :
// Template member function, because it is not always trivial
// or convenient to explicitly mention the typenames in the
// strategy-struct itself.
// Types can be all three different. Therefore it is
// not implemented (anymore) as "segment"
template <typename coordinate_type, typename promoted_type, typename P1, typename P2, typename P>
static inline promoted_type side_value(P1 const& p1, P2 const& p2, P const& p)
{
coordinate_type const x = get<0>(p);
coordinate_type const y = get<1>(p);
coordinate_type const sx1 = get<0>(p1);
coordinate_type const sy1 = get<1>(p1);
coordinate_type const sx2 = get<0>(p2);
coordinate_type const sy2 = get<1>(p2);
promoted_type const dx = sx2 - sx1;
promoted_type const dy = sy2 - sy1;
promoted_type const dpx = x - sx1;
promoted_type const dpy = y - sy1;
return geometry::detail::determinant<promoted_type>
(
dx, dy,
dpx, dpy
);
}
template <typename P1, typename P2, typename P>
static inline int apply(P1 const& p1, P2 const& p2, P const& p)
{
typedef typename boost::mpl::if_c
<
boost::is_void<CalculationType>::type::value,
typename select_most_precise
<
typename select_most_precise
<
typename coordinate_type<P1>::type,
typename coordinate_type<P2>::type
>::type,
typename coordinate_type<P>::type
>::type,
CalculationType
>::type coordinate_type;
// Promote float->double, small int->int
typedef typename select_most_precise
<
coordinate_type,
double
>::type promoted_type;
promoted_type const s = side_value<coordinate_type, promoted_type>(p1, p2, p);
promoted_type const zero = promoted_type();
return math::equals(s, zero) ? 0
: s > zero ? 1
: -1;
}
};
#ifndef DOXYGEN_NO_STRATEGY_SPECIALIZATIONS
namespace services
{
template <typename CalculationType>
struct default_strategy<cartesian_tag, CalculationType>
{
typedef side_by_triangle<CalculationType> type;
};
}
#endif
}} // namespace strategy::side
}} // namespace boost::geometry
#endif // BOOST_GEOMETRY_STRATEGIES_CARTESIAN_SIDE_BY_TRIANGLE_HPP
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