CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Yifei Li wrote:
> Hi all,
>
> I'm new to CGAL and confused by how different examples declare CGAL kernels.
>
> For example, what's the different between the following declarations:
>
> typedef Cartesian<double> K
> typedef Exact_predicates_inexact_construction_kernel K
>
> Is Exact_predicates_inexact_construction a super set of Cartesian<double>? 

Currently,
Exact_predicates_inexact_construction_kernel is
Filtered_kernel< Simple_cartesian<double> >

Have a look here for more details:
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Kernel_23_ref/Class_Filtered_kernel.html#Index_anchor_339



> I tried using Circle.has_on_boundary predicate with Cartesian<double>, I 
> also got the correct answer
The fact that on the cases you tested this predicate with this kernel
returns the correct answer does not mean that this will always be the
case. The problem with using such a kernel is that you cannot guarantee 
that the result of a predicate is correct in all the cases (in 
particular in degenerate cases).

Have a look here for more information:
http://www.cgal.org/philosophy.html

> Thanks
>
> Yifei