Re: Fixing geometic calculation - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Fixing geometic calculation
Date
Msg-id 24011.1249663839@sss.pgh.pa.us
Whole thread Raw
In response to Re: Fixing geometic calculation  (Sam Mason <sam@samason.me.uk>)
Responses Re: Fixing geometic calculation  (Sam Mason <sam@samason.me.uk>)
Re: Fixing geometic calculation  (Paul Matthews <plm@netspace.net.au>)
List pgsql-hackers
Sam Mason <sam@samason.me.uk> writes:
> Sorry, I'm struggling to parse that.  I think it's all the double
> negatives.  Are you saying that HYPOT() should really return zero when
> it's currently giving back would be FPzero?

No, I'm worried about code that supposes that it can divide by (x - y)
after testing that FPeq(x,y) is not true.  point_sl() for instance.

We could perhaps fix those specific issues by testing the difference
explicitly instead of doing it like that.  But there's still the overall
problem of error accumulation ...
        regards, tom lane


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