CGAL users discussion list

[Jean Pierre Charalambos <>]

Hi cgal users,

I'm new to cgal 3.4 and I want to compute the minimal bounding sphere of a 
set 
of spheres. So I just tried to adapt the min_sphere_of_spheres_d_3.cpp 
example, but I have a problem when trying to convert the sphere types (radius 
and center) to double types. I suppose this is a basic question, but I have 
read the faqs and I googled a lot without success. My code is:

typedef CGAL::Gmpq FT;
typedef CGAL::Cartesian<FT> K;
typedef CGAL::Min_sphere_of_spheres_d_traits_3<K,FT> Traits;
typedef CGAL::Min_sphere_of_spheres_d<Traits> Min_sphere;
typedef K::Point_3  Point;
typedef Traits::Sphere  Sphere;

//after checking in the spheres in ms and computing the minimal sphere (just 
like in the example) I attempted the conversion as follows:

radius = CGAL::to_double(ms.radius());

However, I got the following compilation error:

cannot convert ‘CGAL::Null_tag’ to ‘double’ in assignment

If I use "typedef double FT" (instead of typedef CGAL::Gmpq FT) and retrieve 
the radius with "radius = ms.radius()" the code compiles (and it actually 
runs 
perfectly in cgal3.3), but I get the following errror at running time:

terminate called after throwing an instance of 'CGAL::Assertion_exception'
  what():  CGAL ERROR: assertion violation!
Expr: -CGAL_IA_MUL(-1.1, 10.1) != CGAL_IA_MUL(1.1, 10.1)
File: /usr/include/CGAL/Interval_nt.h
Line: 154
Explanation: Wrong rounding: did you forget the -frounding-math option if you 
use GCC?
Aborted

Thank you in advanced for your suggestions,

Jean Pierre
-- 
You don't become a failure until you're satisfied with being one.