[J3] C TS 18661

[Van Snyder]

On Wed, 2019-01-30 at 11:09 -0500, Steve Lionel via J3 wrote:
> On 1/30/2019 10:43 AM, Vipul Parekh via J3 wrote:
> >> acosd
> >> asind
> >> atand
> >> atan2d
> >> expm1
> >> logp1 (or log1p)
> >> rsqrt
> >> ..
> > Why not add all these to the Fortran standard?  Why won't this be a no-brainer?
> >
> J3 already has the degree intrinsics on its list for the next standard 
> (18-139r1, 18-272r1), largely due to their widespread existing 
> implementation and use.  A case for the other intrinsics mentioned would 
> have to be made using different arguments. (I am not a mathematician, 
> but I had never heard of expm1 or logp1, and don't recall a single 
> request for rsqrt from a customer during my decades as a vendor. This is 
> not an argument against them, just saying I'd want to see a stronger 
> case than FOMO.)

I had forgotten that the inverse degree intrinsics are already under
consideration.  My recollection was only the forward ones.  So we don't
need to bring them up again.

If processors exploit rsqrt (either instructions or the fast algorithm),
that's not an issue.

The only ones left from my list of yesterday are expm1 and logp1.

There was resistance to adding intrinsic bessel functions, error
function, and 2-norm functions.  But Anton's survey results show they're
popular.

Developers of engineering and scientific software are frequently pressed
for time, and just go get math software from netlib.  They don't pester
vendors because they know results will take longer than their project.
Having intrinsic functions is helpful, even if they don't agitate for
them.