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// Copyright (c) 2000 Utrecht University (The Netherlands),
// ETH Zurich (Switzerland), Freie Universitaet Berlin (Germany),
// INRIA Sophia-Antipolis (France), Martin-Luther-University Halle-Wittenberg
// (Germany), Max-Planck-Institute Saarbruecken (Germany), RISC Linz (Austria),
// and Tel-Aviv University (Israel). All rights reserved.
//
// This file is part of CGAL (www.cgal.org); you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public License as
// published by the Free Software Foundation; version 2.1 of the License.
// See the file LICENSE.LGPL distributed with CGAL.
//
// Licensees holding a valid commercial license may use this file in
// accordance with the commercial license agreement provided with the software.
//
// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
//
// $URL: svn+ssh://scm.gforge.inria.fr/svn/cgal/branches/CGAL-3.2-branch/Intersections_2/include/CGAL/Line_2_Line_2_intersection.h $
// $Id: Line_2_Line_2_intersection.h 31166 2006-05-17 16:30:56Z spion $
//
//
// Author(s) : Geert-Jan Giezeman
#ifndef CGAL_LINE_2_LINE_2_INTERSECTION_H
#define CGAL_LINE_2_LINE_2_INTERSECTION_H
#include <CGAL/config.h>
#include <CGAL/Line_2.h>
#include <CGAL/Point_2.h>
#include <CGAL/kernel_assertions.h>
#include <CGAL/number_utils.h>
#include <CGAL/Object.h>
CGAL_BEGIN_NAMESPACE
namespace CGALi {
template <class K>
class Line_2_Line_2_pair {
public:
enum Intersection_results {NO_INTERSECTION, POINT, LINE};
Line_2_Line_2_pair() ;
Line_2_Line_2_pair(typename K::Line_2 const *line1,
typename K::Line_2 const *line2);
~Line_2_Line_2_pair() {}
Intersection_results intersection_type() const;
bool intersection(typename K::Point_2 &result) const;
bool intersection(typename K::Line_2 &result) const;
protected:
typename K::Line_2 const* _line1;
typename K::Line_2 const * _line2;
mutable bool _known;
mutable Intersection_results _result;
mutable typename K::Point_2 _intersection_point;
};
template <class K>
inline bool do_intersect(
const typename CGAL_WRAP(K)::Line_2 &p1,
const typename CGAL_WRAP(K)::Line_2 &p2,
const K&)
{
typedef Line_2_Line_2_pair<K> pair_t;
pair_t pair(&p1, &p2);
return pair.intersection_type() != pair_t::NO_INTERSECTION;
}
template <class K>
Object
intersection(const typename CGAL_WRAP(K)::Line_2 &line1,
const typename CGAL_WRAP(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 Object();
case is_t::POINT: {
typename K::Point_2 pt;
linepair.intersection(pt);
return make_object(pt);
}
case is_t::LINE:
return make_object(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>
Line_2_Line_2_pair<K>::Line_2_Line_2_pair()
{
_line1 = 0;
_line2 = 0;
_known = false;
}
template <class K>
Line_2_Line_2_pair<K>::Line_2_Line_2_pair(
typename K::Line_2 const *line1, typename K::Line_2 const *line2)
{
_line1 = line1;
_line2 = line2;
_known = false;
}
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 (_known)
return _result;
RT nom1, nom2, denom;
// The non const this pointer is used to cast away const.
_known = true;
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>
bool
Line_2_Line_2_pair<K>::intersection(typename K::Point_2 &pt) const
{
if (!_known)
intersection_type();
if (_result != POINT)
return false;
pt = _intersection_point;
return true;
}
template <class K>
bool
Line_2_Line_2_pair<K>::intersection(typename K::Line_2 &l) const
{
if (!_known)
intersection_type();
if (_result != LINE)
return false;
l = *_line1;
return true;
}
} // namespace CGALi
template <class K>
inline bool do_intersect(
const Line_2<K> &p1,
const Line_2<K> &p2)
{
typedef typename K::Do_intersect_2 Do_intersect;
return Do_intersect()(p1, p2);
}
template <class K>
Object
intersection(const Line_2<K> &line1, const Line_2<K> &line2)
{
typedef typename K::Intersect_2 Intersect;
return Intersect()(line1, line2);
}
CGAL_END_NAMESPACE
#endif
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