CGAL users discussion list

[Eric Berberich <>]

Eric Berberich wrote:
> muhibur wrote:
> > Hi,
> > Here is the relevant portion of the code. Here "curves" is a vector of
> > pointers to a structure "Projected_Curve", each of which contains the
> > description of a curve to be inserted into the arrangement.
> > void insert_into_arrangement()
> > {
> >     int i,size;
> >     Rational R, S, T, U, V, W;
> >     std::list<Conic_arc_2> arcs;
> >
> >     for(i=0;i<curves.size();i++)
> >     {
> >         Projected_Curve * pc =     curves[i];       
> >
> >         R = pc->R;
> >         S = pc->S;
> >         T = pc->T;
> >         U = pc->U;
> >         V = pc->V;
> >         W = pc->W;
> >
> >         Conic_arc_2 c = Conic_arc_2(R,S,T,U,V,W);
> >         arcs.push_back(c);
> >     }   
> >     insert_curves(arr, arcs.begin(), arcs.end());
> > }
> >
> > The curve data I mentioned in my last mail was output using <<. What I
> > outputted was the r,s,t,u,v,w attributes from the structure
> > "Projected_Curve". These are the 'double' versions of R,S,T ...
> >
> > The error does not occur in the line "Conic_arc_2 c =
> > Conic_arc_2(R,S,T,U,V,W);" but in the insert_curves routine. The includes
> > and typedefs are exactly same as the example conic.cpp provided in the 
> > CGAL
> > distribution.

The conic c2(1.0, 52.2892, 12.098, 542.364, 4855.69, 115594.0) is an 
"empty" one. That is, the vanishing set of the defining polynomial is 
empty. Unfortunately, it seems that Make_x_monotone_2 (that is called 
for each curve before actually inserting it's x-monotone subpieces) 
stumbled upon it. In particular, source and target are set to (0,0), 
which results in the error you see. But, actually and correctly, it 
should not be tried to construct any x-monontone curve in this curve ...

eriC