Consider adding public PyLong_GetSign() function

[skirpichev]

Feature or enhancement

Proposal:

Currently there is no way to determine the sign of the PyLongObject value and CPython extensions use private macroses like _PyLong_IsNegative(): https://github.com/aleaxit/gmpy/blob/eb8dfcbd84abcfcb36b4adcb0d5c6d050731dd75/src/gmpy2_convert_gmp.c#L56

PyLong_Sign() will offer GMP-like API to do this.

This was suggested before: #102471 (comment)

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-116560: Add PyLong_GetSign() public function #116561

[serhiy-storchaka]

I think that PyLong_IsPositive(), PyLong_IsNegative() and PyLong_IsZero() are more useful in practice, but there may also be a smaller need for PyLong_Sign(). I suggest to implement the former functions first, and then look if there are enough use cases left for the latter.

[skirpichev]

I worry only on PyLongObject input (probably as most consumers of API). Why three functions better then one? (Disclaimer: API, produced by C-API WG seems too generic for me; IMHO _PyLong_Sign() interface fits use cases in real world much better.)

[vstinner]

Implemented in commit 61d3ab3

[skirpichev]

@vstinner, if I correctly interpret voting, PyLong_IsPositive/Negative/Zero API got support.

Lets reopen this to track implementation, as it's part of the same API?

[serhiy-storchaka]

It is better to open a separate issue.