CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

On 11/03/2012 07:22 PM, Sebastian Hegler wrote:
> Hello!
>
> The attached patch exposes the GeomTraits of the AABB_traits class, which is 
> basically the CGAL kernel type used for the instantiation, by using a public 
> typedef.
> This one-liner makes my work a lot easier. If you find it worthy, feel free 
> to include it in the CGAL library.
I think the main reason why what you suggest is not done in CGAL,
is that all types that AABB_traits must provide are described in the 
AABBGeomTraits concept [1], and all those types are then exposed in
AABB_traits as a model of AABBTraits [1].

This means that you need this typedef to use other types not required
by the concept, which implies that your algorithm might not work with
an alternative traits for the AABB_tree (which is perfectly fine if you
don't expect to change the traits at some point).

If you really need it and want to use official CGAL, I suggest to get 
GeomTraits using a partial specialization of a class, something like:

template <class T>
struct Get_geom_traits;

template<typename GeomTraits, typename AABB_primitive>
struct Get_geom_traits< CGAL::AABB_traits<GeomTraits,AABB_primitive> >
{
  typedef GeomTraits type;
};



[1] 
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/AABB_tree_ref/Concept_AABBTraits.html

[2] 
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/AABB_tree_ref/Concept_AABBGeomTraits.html

> Yours,
> Sebastian