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From: Paul Rubin <no.email@nospam.invalid>
Newsgroups: comp.lang.forth
Subject: Re: Parsing timestamps?
Date: Thu, 10 Jul 2025 18:40:32 -0700
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minforth <minforth@gmx.net> writes:
> Kahan was also overly critical of dynamic Unum/Posit formats.
> Time has shown that he was partially wrong:
> https://spectrum.ieee.org/floating-point-numbers-posits-processor

I don't feel qualified to draw a conclusion from this.  I wonder what
the numerics community thinks, if there is any consensus.  I remember
being dubious of posits when I first heard of them, though Kahan
probably influenced that.  I do know that IEEE 754 took a lot of trouble
to avoid undesirable behaviours that never would have occurred to most
of us.  No idea how well posits do at that.  I guess though, given the
continued attention they get, they must be more interesting than I had
thought.

I saw one of the posit articles criticizing IEEE 754 because IEEE 754
addition is not always associative.  But that is inherent in how
floating point arithmetic works, and I don't see how posit addition can
avoid it.  Let a = 1e100, b = -1e100, and c=1.  So mathematically,
a+b+c=1.  You should get that from (a+b)+c in your favorite floating
point format.  But a+(b+c) will almost certainly be 0, without very high
precision (300+ bits).