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IEEE float co-processors
- To: firstname.lastname@example.org (Richard Fateman)
- Subject: IEEE float co-processors
- From: "Scott E. Fahlman" <Fahlman@C.CS.CMU.EDU>
- Date: Tue, 28 Jan 1986 12:56:00 -0000
- Cc: common-lisp@SU-AI.ARPA
- In-reply-to: Msg of 28 Jan 1986 02:08-EST from fateman at dali.berkeley.edu (Richard Fateman)
- Sender: FAHLMAN@C.CS.CMU.EDU
I believe the standard should allow the processor to perform all floating
point arithmetic computations in highest precision, and not require
multiple conversions (from short to single to double to long).
The paragraph which allows rearrangement or conversion to the longest
format IN THE EXPRESSION is not flexible enough to quite allow this.
This sounds like a good proposal, and it wouldn't break anyone's code to
implement it. I think that all we need is a clarification that says
that a compiler is allowed to do whatever it wants to in handling
the precision of intermediate arithmetic results, as long as any outputs
finally accessible to the user are of the specified type and as long as
precision is at least as good as you would get by doing the obvious
coercions at each step.
My only concern is that the interpreter would probably be stuck with
doing the coercions at each step, and therefore might get a slightly
different (less precise) answer than the compiler would come up with.
Would that bother anyone? (Not me, but I only look at the first two