gh-132908: check the return type of isnormal() and issubnormal()

[picnixz]

I've actually stumbled upon the isnormal() C11 requirements (which I assume are the same as issubnormal() ones but I don't have a C23 copy) and I think we can add those checks (I first thought about returning the integer value given by signbit but in C++, it returns a bool instead of just an integer [on some implementations it gives the power of 2 representing the sign bit].

• Issue: Have math.isnormal() and, perhaps, math.issubnormal()? #132908

[skirpichev]

Looks good, but we don't have similar checks for other predicates, e.g. isfinite(). That's why I don't sure we should add such checks.

But it's up to you. BTW, probably you can remove comments - we have documentation, right?

[picnixz]

That's why I don't sure we should add such checks.

Oh! Ok makes sense. Let's not burden the already existing tests. I've added it in signbit because signbit may return the corresponding power-of-two if there is a sign bit. But I think it's the only one that is not named "isXXX()" and that returns a boolean.

But it's up to you. BTW, probably you can remove comments - we have documentation, right?

Right. I actually wanted to add a comment in the tests in case we change the return value for some reason (it could serve as a regression test as well). I don't want to burden the online docs with those implementation details (in C++ for instance, it's a boolean that is returned, so depending on the page of cppreference you land, you may be like "why are they explaining this?").

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Sorry for the noise! I'll keep the check in the signbit PR because of the lack of the is prefix but won't merge this one.

[picnixz]

@skirpichev Btw, do you remember if we have an issue about positional-only arguments in math.* ? all functions are positional-only but I don't remember what we decided.

[skirpichev]

do you remember if we have an issue about positional-only arguments in math.* ? all functions are positional-only but I don't remember what we decided.

@picnixz, I'm not sure we have an issue about this. Perhaps, you are about this pr: #131886 ?

In similar way we could change signatures in the math module. The cost is a small regression in processing arguments. (Perhaps, it could be solved.)