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Comments on clause 9. Recommended operations in draft 1.6.0
(a) Leave Inexact completely undefined, or
(b) Require correct Inexact indication for transcendental functions,
and permit overindication for the simple algebraic functions.
Not sure what (a) means: it applies only to 9, right? We keep 7.6?
Then I'm OK.
I meant in the context of clause 9, of course!
(b) is better, but it needs to list explicitely those which have a
shall and those which have a should.
Agreed.
In the list of domains (D.4), I would add a comment that the FP domain
of tan x does not have holes (because the mathematical holes are not
representable input values).
It depends what you mean by hole. In some (pathological?) formats, the
tan of some values could overflow, and be defined (unambiguously) as
+infty or -infty. I'm sure it doesn't happen for binary64, but it needs
to be checked for other formats as well.
Precisely my point: for rational input, overflow determines the sign of
infinity, so the input is a valid member of the domain, and there is no
hole, in the sense that there is no input value for which the result would
be undefined. The only invalid inputs for tan x are -Inf and +Inf, at the
ends of the domain (which is why I don't call them "holes").
Michel.
Sent: 2008-02-01 18:40:32 UTC