CGAL users discussion list

[Monique Teillaud <>]

Le 15/08/12 09:36, Alex Tsui a écrit :
> Hi,
>
> I am using Exact_circular_kernel_2 and I would like to construct a line
> segment that exactly passes through two Circular_arc_point_2's. It looks
> like I have a choice between a CircularKernel::Segment_2 or a
> CircularKernel::Line_arc_2. However, Segment_2's coordinate type (FT)
> doesn't match the arc point's coordinate type (Root_of_2).

> It also seems
> that you can't construct a Line_arc_2 given just two arc points - you
> also need a Line_2 that contains both of the arc points. But like the
> Segment_2, Line_2 uses FT coordinates and I'm not sure how to construct
> one that contains both arc points.

Dear Alex,

There is not always a line with FT coefficients that contains the two 
points (think of the case when the coordinates of the two points are not 
in the same extension field).

So, if you are in such a case, and if you need your points to lie 
exactly on the circle, then as Efi said, you must use a kernel based on 
a number type that handles square roots, and it will be less efficient.

--
Monique Teillaud
INRIA Sophia Antipolis - Méditerranée
http://www.inria.fr/sophia/members/Monique.Teillaud/