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From: Michael S <already5chosen@yahoo.com>
Newsgroups: comp.lang.c,comp.arch
Subject: Re: Radians Or Degrees?
Date: Fri, 15 Mar 2024 14:15:52 +0200
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On Fri, 15 Mar 2024 11:23:45 +0100
Terje Mathisen <terje.mathisen@tmsw.no> wrote:

> Michael, I for the main part agree with you here, i.e. calculating 
> sin(x) with x larger than 2^53 or so, is almost certainly stupid.
> 
> Actually using and depending upon the result is more stupid.
> 
> OTOH, it is and have always been, a core principle of ieee754 that
> basic operations (FADD/FSUB/FMUL/FDIV/FSQRT) shall assume that the
> inputs are exact (no fractional ulp uncertainty), and that we from
> that starting point must deliver a correctly rounded version of the
> infinitely precise exact result of the operation.
> 
> Given the latter, it is in fact very tempting to see if that basic 
> result rule could be applied to more of the non-core operations, but
> I cannot foresee any situation where I would use it myself: If I find 
> myself in a situation where the final fractional ulp is important,
> then I would far rather switch to doing the operation in fp128.
> 
> Terje
>

To make it less tempting, you could try to push for inclusion of
rsqrt() into basic set. Long overdue, IMHO.

Right now, I can't think of any other transcendental that I really want
to elevate to higher status. It seems to me that elevation of log2(x)
and of 2**x will do no harm, but I am not sure about usefulness.