| From: | "Ken Hirsch" <kahirsch(at)bellsouth(dot)net> |
|---|---|
| To: | <pgsql-hackers(at)postgresql(dot)org>, <pgsql-ports(at)postgresql(dot)org> |
| Subject: | Re: Geometry test on NetBSD (was Re: [HACKERS] RC1?) |
| Date: | 2002-11-20 17:02:38 |
| Message-ID: | OE54RmUBdiAG95OIKaO000016a7@hotmail.com |
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| Lists: | pgsql-hackers pgsql-ports |
Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> wrote:
>
> Tom, can you clarify why -0 is valid. Is it for _small_ near zero
> values that are indeed negative?
>
"Branch Cuts for Complex Elementary Functions, or Much Ado About
Nothing's Sign Bit" W. Kahan; ch. 7 in _The State of the Art in
Numerical Analysis_ ed. by M. Powell and A. Iserles 1987 Oxford.
Explains how proper respect for -0 eases implementation of conformal
maps of slitted domains arising in studies of flows around obstacles.
Kahan was one of the most important people behind the floating point
standard and won the 1989 Turing Award for his work in numerical computing.
http://www.cs.berkeley.edu/~wkahan/ieee754status/754story.html
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