Re: Floating point comparison inconsistencies of the geometric types

Kevin Grittner <kgrittn(at)gmail(dot)com> writes:
> On Wed, Jun 1, 2016 at 8:08 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> Figuring out what to do about it is harder. Your proposal seems to be
>> to remove them except where we need the fuzzy behavior, which doesn't
>> sound unreasonable, but I don't personally understand why we need it
>> in some places and not others.

> +1

> My first inclination is to remove those macros in version 10, but
> it would be good to hear from some people using these types on what
> the impact of that would be.

As I understand it, the key problem is that tests like "is point on line"
would basically never succeed except in the most trivial cases, because of
roundoff error. That's not very nice, and it might cascade to larger
problems like object-containment tests failing unexpectedly. We would
need to go through all the geometric operations and figure out where that
kind of gotcha is significant and what we can do about it. Seems like a
fair amount of work :-(. If somebody's willing to do that kind of
investigation, then sure, but I don't think just blindly removing these
macros is going to lead to anything good.

Also, I suppose this means that Robert promises not to make any of his
usual complaints about breaking compatibility? Because we certainly
would be.

regards, tom lane