CGAL users discussion list

[Sylvain Pion <>]

Alejandro Aragon a écrit :
> Hi, no one has replied to my post yet, so I decided to send it again in 
> case someone will.

Wrong decision : you should have decided to read the FAQ, for example.


> I'm trying to check how the oriented_side() function 
> works for a line. I
> created a very simple example, where a point should lie on a line, but it
> doesn't. The program is as follows:
>
> #include <CGAL/Cartesian.h>
> #include <iostream>
>
> using std::cout;
> using std::endl;
>
> int main() {
>
> typedef CGAL::Cartesian<double> KernelType;
> typedef KernelType::Point_2 PointType;
> typedef KernelType::Line_2 LineType;
>
>
> PointType p(0.034,0.006);
> cout<<"point -> "<<p<<endl;
>
> LineType l(-0.004, 0.004, 0.000112);
> cout<<"line -> "<<l<<endl;
>
> CGAL::Oriented_side test = l.oriented_side(p);
>
> if ( test == CGAL::ON_POSITIVE_SIDE ) {
> cout<<"point on positive side"<<endl;
> } else if ( test == CGAL::ON_NEGATIVE_SIDE ) {
> cout<<"point on negative side"<<endl;
> } else {
> cout<<"point over line"<<endl;
> }
>
> return 0;
> }
>
> The output of this little program is:
>
> point -> 0.034 0.006
> line -> -0.004 0.004 0.000112
> point on negative side
>
> Can someone tell me what is happening here? The point should not be on the
> negative side. Thank you all.


--
Sylvain Pion
INRIA Sophia-Antipolis
Geometrica Project-Team
CGAL, http://cgal.org/

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