Re: Fixing geometic calculation

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Sam Mason <sam(at)samason(dot)me(dot)uk>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Fixing geometic calculation
Date: 2009-08-07 16:50:39
Message-ID: 24011.1249663839@sss.pgh.pa.us
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Sam Mason <sam(at)samason(dot)me(dot)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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