CGAL users discussion list

[Alejandro Aragon <>]

There is nothing in the FAQ that prevents people from reposting a  
message, thanks for your helpful reply.

On Jul 23, 2008, at 10:38 AM, Sylvain Pion wrote:

> 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/