CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

On 04/23/2012 02:55 PM, 

 wrote:
> I'm trying the add one property to the point class.
>
> By help from  StackOverflow I was directed to Manual Chapter 11.5 Extensible
> Kernel using this I wrote the code below.
>
> The code  will not compile and I get the error:
> ‘typename CGAL::Extended_homogeneous::Base’ names
> 'CGAL::Extended_homogeneous::Base’, which is not a class template|
>
> == CODE ==
> #include<CGAL/Extended_homogeneous.h>
>
> template<  typename K_, typename K_Base>
> class My_base  : public K_Base::template Base<K_>::Type
> {
>    typedef typename K_Base::template Base<K_>::Type   OldK;
>
> public:
>    typedef K_                               Kernel;
>
>    template<  typename Kernel2>
>    struct Base { typedef My_base<Kernel2, K_Base>   Type; };
>   };
>
> template<  typename RT_>
> struct MyKernel  : public CGAL::Type_equality_wrapper<My_base<MyKernel<RT_>,
> CGAL::Homogeneous<RT_>  >,  MyKernel<RT_>  >
> {};
>
> #include<CGAL/Nef_polyhedron_3.h>
> typedef MyKernel<CGAL::Gmpz>      Kernel;
>
> typedef CGAL::Nef_polyhedron_3<Kernel>    Nef_Polyhedron;
> typedef Nef_Polyhedron::Plane_3  Plane;
>
> int main()
> {
>    Nef_Polyhedron half_space(Plane(1,1,1,1), Nef_Polyhedron::EXCLUDED);
>
>    return 0;
> }
> ====
>
> If the inhertiance is changed to "public K_Base::Base::template B<K_>::Type" 
> it
> will compile but Then I miss the propeties from Extentensions I guess? Because
> I get the error "Constructor not available for this kernel" when I run the
> program.

The point constructors are not changed by this mechanism. This means 
that only those documented are available. If you want to initialize your 
extra data, you need to first create an object of type My_point and then 
init a point of type MyKernel::Point_3 with it.

The class in the kernel is a kind of interface while My_point is the
representation.

Sebastien.