CGAL users discussion list

["Max" <>]

Hello

I need to do some coordinates transformation between severl 3d coordinate
frames. At first I wrote the following code to do the transformation,

template<typename Vector_3>
CGAL::Aff_transformation_3<typename Vector_3::R> MakeUserCoordSysFromVectors(
        const Vector_3& x, const Vector_3& y, const Vector_3& z )
{
        // make a transformation from global/default coord system
        // to the user/local system specified by the x/y/z *UNIT*
        // vectors denoting the user system's x/y/z axis
        return CGAL::Aff_transformation_3<Kernel>
                (x.x(), x.y(), x.z(),
                y.x(), y.y(), y.z(),
                z.x(), z.y(), z.z());
}

but I got a compiler error. To have the code compiled, I changed the code
to this:

template<typename Vector_3>
CGAL::Aff_transformation_3<typename Vector_3::R> MakeUserCoordSysFromVectors(
        const Vector_3& x, const Vector_3& y, const Vector_3& z )
{
        return CGAL::Aff_transformation_3<Kernel>
                (CGAL::to_double(x.x()), CGAL::to_double(x.y()), 
CGAL::to_double(x.z()),
                CGAL::to_double(y.x()), CGAL::to_double(y.y()), 
CGAL::to_double(y.z()),
                CGAL::to_double(z.x()), CGAL::to_double(z.y()), 
CGAL::to_double(z.z()));
}

yes, it got compiled and worked ok. But I think it's not good enough -
for any exact kernel, an conversion to double and then back may lose
the should-have exactness. How to get rid of this drawback? Is there
any other solution more elegant?

Thanks for any help.

B/Rgds
Max