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- To: labrea!common-lisp%sail@labrea.Stanford.EDU
- Subject: LEAST-POSITIVE-<mumble>-FLOAT
- From: Jon L White <edsel!jonl@labrea.Stanford.EDU>
- Date: Fri, 22 Jan 88 22:15:21 PST
Does anyone care what values these "constants" actually take on? that is,
does anyone use then in any context other than test suites?
CLtL p231 says that this number should be the "number closest in value to
(but not equal to) zero provided by the implementation." In those
implementations supporting IEEE-like denormalized numbers, a question
arises: are denormalized numbers "provided", in the sense required?
Of the four such implementations I've checked, half set this constant
to the least normalized number, and half set it to the least denormalized
Supporting the former is the fact that IEEE hardware, when traps are
enabled, will signal an underflow trap whenever a result would be less
than the least normalized number. Supporting the latter is the fact
that under at least mode of operation of the hardware, denormalized
numbers are "provided" by the implementation.
-- JonL --