CGAL users discussion list

[Sylvain Pion <>]

Alejandro Aragon a écrit :
> Naive???? Try to represent 0.1 exactly using a double precision type! 

I said doubles are real, I did not say that reals are all representable as 
double.
I guess we interpret "mathematical sense" differently.

> Then you'll realize that as soon as you start using an inexact type, the 
> strict "mathematical sense" Andreas was talking about really goes away...
>
> I write a GFEM library and as you may know, as soon as you don't use 
> standard FEM you need heavy computation involving geometry. A library 
> should be written in a way that naive users as me (as you pointed out) 
> would expect a point (usually represented by double types) to lie on top 
> of a line within the same tolerance as the inexact type.

I would be surprised if it was possible to provide a relatively complete
and consistent model, that provides this property, apart from the exact
geometric computation road.

--
Sylvain Pion
INRIA Sophia-Antipolis
Geometrica Project-Team
CGAL, http://cgal.org/