[Cfp-interest] WG14 IEEE 754-C binding meeting minutes 2018/07/25

[Jim Thomas]

David,

I recall 754 discussing the special cases for rootn, but don’t remember if the discrepancy (below) with cfp was mentioned. If it was known and 754 decided its current specification is better, I wouldn’t be inclined to reopen the issue with 754.

- Jim Thomas

> On Aug 23, 2018, at 3:34 PM, Jim Thomas <jaswthomas at sbcglobal.net> wrote:
> 
>>> rootn - 
>>> replace cfp rootn(+/-inf,n) with
> I think cfp and 754 agree except for rootn(-inf, n) for even n > 0:
> 
> cfp says it’s the same as rootn(-0, n) for even n < 0 (without div-by-zero), which cfp and 754 both say is +inf.
> 754 says it's qNaN with invalid.
> 
> We can ask 754 to review/confirm this case. As usual, cfp needs to match 754. If cfp needs to change this case, it seems better to list out the cases for rootn(+/-inf, n) like 754 does, rather than relay on identity with rootn(+/-0, -n) .

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