CGAL users discussion list

[Andreas Fabri <>]

Thomas Zangl - Home wrote:
>  
> Hi!
>
> > > How are the constructions filtered? Can you please give me an example?
> > When you perform an orientation test for three lazy points
> > it is first performed on the approximate points with double intervals.
> > If this cannot been done the exact versions of the points are
> > computed by applying the exact constructions of the DAG.
>
> I thought an orientation test is a predicate not a construction? I
> assumed that a construction ''computess'' a new geometric object like:
> mySegment = dt.dual(myDelaunayFacet) (dual method of a Delaunay
> triangulation).
>
> What is the exact difference between a predicate and a construction?
>
> Thank you!
>
> Best regards,

Hi Thomas,

Did you read   "A Generic Lazy Evaluation Scheme for Exact Geometric 
Computations"
Sylvain Pion and Andreas Fabri,
In Proc. 2nd Library-Centric Software Design, pages 75-84, Portland, Oregon, 
2006.

ftp://ftp-sop.inria.fr/geometrica/pion/publis/lazy-kernel.pdf

andreas