sinpi etc. is also is also part of the Fortran 2023 standard.
So, NumPy would seem more appropriate.
On Fri, 12 Jun 2026 at 22:25, Jeff Epler <[email protected]
<mailto:[email protected]>> wrote:
__
How is it typically decided whether some array function goes in
numpy or scipy?
On Tue, Jun 9, 2026, at 11:08 AM, Lucas Colley via NumPy-Discussion
wrote:
There was a proposal to add these to `scipy.special`:
https://discuss.scientific-python.org/t/rfc-add-sinpi-cospi-tanpi-and-cotpi-functions-to-special/1193
<https://discuss.scientific-python.org/t/rfc-add-sinpi-cospi-tanpi-and-cotpi-functions-to-special/1193>.
There are existing implementations at
https://github.com/scipy/xsf/blob/main/include/xsf/trig.h
<https://github.com/scipy/xsf/blob/main/include/xsf/trig.h> , with
`sinpi` and `cospi` exposed to SciPy (privately) at
https://github.com/scipy/scipy/blob/main/scipy/special/xsf_wrappers.h#L394-L396
<https://github.com/scipy/scipy/blob/main/scipy/special/xsf_wrappers.h#L394-L396>.
We should probably decide whether these best belong in `numpy` or
`scipy.special`, and only expose them in one of the two.
Cheers,
Lucas
On 9 Jun 2026, at 16:23, Jerome Kieffer <[email protected]
<mailto:[email protected]>> wrote:
I like the idea !
On Mon, 08 Jun 2026 08:59:24 -0500
"Jeff Epler" <[email protected]
<mailto:[email protected]>> wrote:
In a recently merged PR
(https://github.com/python/cpython/pull/150555
<https://github.com/python/cpython/pull/150555>), CPython has
added a family of "*pi" functions to the math module, which take
half-turn arguments instead of radians. One reason these
functions are advantageous is that it's easy to provide the
property that `sinpi(n/2)` is exact for all integers n, while
`sin(pi*n)` is never exactly equal to the mathematical ideal
except for n=0.
These functions are recommended by IEEE754-2019 and standardized
in C23 Annex G. (note: I'm reading C23 draft revised 2023-01-24,
not the final standard document; and I do not have IEEE754-2019).
C23 and CPython only added the real-valued versions of these
functions, but C23 "future library directions" notes that
identifiers like `csinpi` are "potentially reserved identifiers."
Since CPython only requires C11, CPython includes
implementations of these functions for when the underling
platform library does not provide it. These implementations work
by performing special case handling & range reduction, followed
by a call to the standard trig function with a scaled argument
(in the case of forward functions) or scaling of the result (in
the case of inverse/arc functions).
I am interested in doing the numpy implementation, however I
have never done core numpy work before. If there is interest
from the project, I would like to initially offer a PR
containing a single function such as `sinpi` and then complete
the others following numpy core developer feedback.
Thanks,
Jeff
PS I notice via the archives that there are occasional "New
Contributors' Hour" meetings. Is the next one scheduled yet?
--
Jérôme Kieffer
tel +33 476 882 445
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