_Py_c_sum, _Py_c_diff, etc - were removed from Python.h

[skirpichev]

See #106339 and #106320. But these functions are documented as public: https://docs.python.org/3/c-api/complex.html#complex-numbers-as-c-structures

I think c38c666 should be partially reverted and _Py_c_abs - documented.

On another hand, quick github search shows very little examples of using above functions. See also #106320 (comment). So, in a long term I propose to deprecate this API and related functions (PyComplex_FromCComplex/PyComplex_AsCComplex). Who knows, maybe someday we could use <complex.h>...

Linked PRs

• gh-112019: reversion of removal _Py_c_* functions in #106339 #112021
• gh-112019: Add Py_complex_abs() function #112107

[skirpichev]

CC @vstinner

[vstinner]

If these functions are useful, I would prefer to make them public.

Previous discussion about this private API: #106320 (comment)