CGAL users discussion list

["Laurent Rineau (GeometryFactory)" <>]

Le jeudi 03 septembre 2009 16:33:53, Bernd Gaertner a écrit :
> Genís wrote:
> > CGAL error:
> > precondition violation!
> > Expr: comp_f(object, nodeP->object) != LARGER
> > File: /usr/include/CGAL/Multiset.h
> > Line: 214
>
> The cause is most likely this line:
> >     typedef CGAL::Cartesian<double>    Kernel;
>
> This is an inexact kernel that comes with no guarantee and whose usage
> may lead to the indicated failures. CGAL has other kernels that do come
> with guarantees, please see the FAQ item at
> http://www.cgal.org/FAQ.html#inexact_NT, and the philosophy page at
> http://www.cgal.org/philosophy.html.

Genis, as you are not at all the only user of CGAL that made that error. Can 
you tell us how you have happened to use that kernel? Did you see occurrences 
of that error-prone kernel in the manual? Where? Have you copied an example 
from CGAL? Which one?

There are only a few cases where the use of CGAL::Cartesian<double> is the 
right choice, and we, CGAL developers, should try to enhance the CGAL manual 
and example so that our users are not guided to make such errors. That is why 
I ask for feedback.

-- 
Laurent Rineau, PhD
Release Manager of the CGAL Project
http://www.cgal.org/
R&D Engineer at GeometryFactory
http://www.geometryfactory.com/