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// Copyright (c) 2000
// Utrecht University (The Netherlands),
// ETH Zurich (Switzerland),
// INRIA Sophia-Antipolis (France),
// Max-Planck-Institute Saarbruecken (Germany),
// and Tel-Aviv University (Israel). All rights reserved.
//
// This file is part of CGAL (www.cgal.org)
//
// $URL: https://github.com/CGAL/cgal/blob/v6.1/Intersections_2/include/CGAL/Intersections_2/Line_2_Line_2.h $
// $Id: include/CGAL/Intersections_2/Line_2_Line_2.h b26b07a1242 $
// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s) : Geert-Jan Giezeman
#ifndef CGAL_INTERSECTIONS_2_LINE_2_LINE_2_H
#define CGAL_INTERSECTIONS_2_LINE_2_LINE_2_H
#include <CGAL/config.h>
#include <CGAL/Line_2.h>
#include <CGAL/kernel_assertions.h>
#include <CGAL/number_utils.h>
#include <CGAL/Intersection_traits_2.h>
namespace CGAL {
class Cartesian_tag;
class Homogeneous_tag;
namespace Intersections {
namespace internal {
template <class K>
class Line_2_Line_2_pair {
public:
enum Intersection_results {NO_INTERSECTION, POINT, LINE, UNKNOWN};
Line_2_Line_2_pair(typename K::Line_2 const *line1,
typename K::Line_2 const *line2)
: _line1(line1), _line2(line2) {}
Intersection_results intersection_type() const;
typename K::Point_2 intersection_point() const;
typename K::Line_2 intersection_line() const;
protected:
typename K::Line_2 const* _line1;
typename K::Line_2 const * _line2;
mutable Intersection_results _result = UNKNOWN;
mutable typename K::Point_2 _intersection_point;
};
template <class K>
inline
typename K::Boolean
do_intersect(const typename K::Line_2& l1,
const typename K::Line_2& l2,
const K&)
{
typedef Line_2_Line_2_pair<K> pair_t;
pair_t pair(&l1, &l2);
return pair.intersection_type() != pair_t::NO_INTERSECTION;
}
template <class K>
typename CGAL::Intersection_traits
<K, typename K::Line_2, typename K::Line_2>::result_type
intersection(const typename K::Line_2 &line1,
const typename K::Line_2 &line2,
const K&)
{
typedef Line_2_Line_2_pair<K> is_t;
is_t linepair(&line1, &line2);
switch (linepair.intersection_type()) {
case is_t::NO_INTERSECTION:
default:
return intersection_return<typename K::Intersect_2, typename K::Line_2, typename K::Line_2>();
case is_t::POINT:
return intersection_return<typename K::Intersect_2, typename K::Line_2, typename K::Line_2>(linepair.intersection_point());
case is_t::LINE:
return intersection_return<typename K::Intersect_2, typename K::Line_2, typename K::Line_2>(line1);
}
}
template <class R, class POINT, class RT>
bool construct_if_finite(POINT &pt, RT x, RT y, RT w, R &, const Cartesian_tag &)
{
typename R::Construct_point_2 construct_point;
typedef typename R::FT FT;
CGAL_kernel_precondition(CGAL_NTS is_finite(x)
&& CGAL_NTS is_finite(y)
&& w != RT(0));
FT xw = FT(x)/FT(w);
FT yw = FT(y)/FT(w);
if (!CGAL_NTS is_finite(xw) || !CGAL_NTS is_finite(yw))
return false;
pt = construct_point(xw, yw);
return true;
}
template <class R, class POINT, class RT>
bool construct_if_finite(POINT &pt, RT x, RT y, RT w, R &, const Homogeneous_tag&)
{
typename R::Construct_point_2 construct_point;
typedef typename R::FT FT;
CGAL_kernel_precondition(CGAL_NTS is_finite(x)
&& CGAL_NTS is_finite(y)
&& w != RT(0));
FT xw = FT(x)/FT(w);
FT yw = FT(y)/FT(w);
if (!CGAL_NTS is_finite(xw) || !CGAL_NTS is_finite(yw))
return false;
pt = construct_point(x, y, w);
return true;
}
template <class R, class POINT, class RT>
inline
bool
construct_if_finite(POINT &pt, RT x, RT y, RT w, const R &r)
{
typedef typename R::Kernel_tag Tag;
Tag tag;
return construct_if_finite(pt, x, y, w, r, tag);
}
template <class K>
typename Line_2_Line_2_pair<K>::Intersection_results
Line_2_Line_2_pair<K>::intersection_type() const
{
typedef typename K::RT RT;
if (_result != UNKNOWN)
return _result;
RT nom1, nom2, denom;
// The non const this pointer is used to cast away const.
denom = _line1->a()*_line2->b() - _line2->a()*_line1->b();
if (denom == RT(0)) {
if (RT(0) == (_line1->a()*_line2->c() - _line2->a()*_line1->c()) &&
RT(0) == (_line1->b()*_line2->c() - _line2->b()*_line1->c()))
_result = LINE;
else
_result = NO_INTERSECTION;
return _result;
}
nom1 = (_line1->b()*_line2->c() - _line2->b()*_line1->c());
if (!CGAL_NTS is_finite(nom1)) {
_result = NO_INTERSECTION;
return _result;
}
nom2 = (_line2->a()*_line1->c() - _line1->a()*_line2->c());
if (!CGAL_NTS is_finite(nom2)) {
_result = NO_INTERSECTION;
return _result;
}
K dummyR;
if (!construct_if_finite(_intersection_point,
nom1, nom2, denom, dummyR)){
_result = NO_INTERSECTION;
return _result;
}
_result = POINT;
return _result;
}
template <class K>
typename K::Point_2
Line_2_Line_2_pair<K>::intersection_point() const
{
if (_result == UNKNOWN)
intersection_type();
CGAL_kernel_assertion(_result == POINT);
return _intersection_point;
}
template <class K>
typename K::Line_2
Line_2_Line_2_pair<K>::intersection_line() const
{
if (_result == UNKNOWN)
intersection_type();
CGAL_kernel_assertion(_result == LINE);
return *_line1;
}
} // namespace internal
} // namespace Intersections
CGAL_INTERSECTION_FUNCTION_SELF(Line_2, 2)
CGAL_DO_INTERSECT_FUNCTION_SELF(Line_2, 2)
} // namespace CGAL
#endif // CGAL_INTERSECTIONS_2_LINE_2_LINE_2_H
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