Re: Fixing geometic calculation

Sam Mason <sam(at)samason(dot)me(dot)uk> writes:
> I would agree with Paul that EPSILON is a hack and probably should be
> removed.

It's a hack but it's dealing with an extremely real problem, namely
the built-in inaccuracy of floating-point arithmetic. You can't just
close your eyes to that and hope that everything will be okay.

A quick look through the geometry sources says that we might not be
critically dependent on anything except the assumption that two values
that aren't FPeq() will have a nonzero difference. (If you think this
is a tautology, you don't know enough about floating point arithmetic
to be qualified to offer an opinion here...) We might be able to base
a tighter comparison procedure on that rule. It would take a lot more
investigation to be sure though.

regards, tom lane