CGAL users discussion list

[Marc Glisse <>]

On Fri, 26 Feb 2016, Frédérik Paradis wrote:

> > You could look at Search_traits_3 (there may be better examples in CGAL, I
> > just picked the first one I found). It handles the difference through
> > typedefs.
>
> IIRC, I tried that but I got strange compilation errors in Ipelet_base
> because I think the way it instantiates some object like Iso_retangles and
> circles.

Try harder? That is the most natural way in CGAL. If you have trouble with 
it, maybe you can ask here with specific code. Maybe there is a real 
obstruction that prevents from using this solution here, but you would 
likely be asked to explain it before integrating code that uses a 
different strategy.

> > One common trick is to compare the square of distances instead of the
> > distances directly, to avoid square roots. Something like d^2 >= s^2*r^2.
>
> But the get d, I have get the distance between the two circles and
> substract the radius of the circles.

The code you showed has:
(distance_vw - 2.*max_rad) > s*max_rad
which I can rewrite:
distance_vw > (s+2)*max_rad
and I can square both sides.

Sure, in some cases removing the square roots can be harder, but it is 
doable.

--
Marc Glisse