feat(collections): add sumOf

[grian32]

Not sure if there should be more tests, couldn't really think of anything else as its a pretty simple function.

Related: #1065

[LionC]

Totally unrelated question now that I am seeing this implemented - should we maybe support bigint?

Edit: As I understand it, bigint supports + without weird caveats, so you would "just" need to add it to the typing of the function to support it. Sounds like an easy win?

[grian32]

Totally unrelated question now that I am seeing this implemented - should we maybe support bigint?

Edit: As I understand it, bigint supports + without weird caveats, so you would "just" need to add it to the typing of the function to support it. Sounds like an easy win?

I'd need some extra checks so sum could start off as bigint instead of number, not sure if that'd hurt performance but I'll push it eitherway. We can benchmark after if it's needed.

Edit: Actually, I'm not really sure how to implement this. as I cant get typescript to really agree since the selector would be a union type and it doesn't like adding that to bigint or number even if i have typeguards

[caspervonb]

Edit: Actually, I'm not really sure how to implement this. as I cant get typescript to really agree since the selector would be a union type and it doesn't like adding that to bigint or number even if i have typeguards

Would have to make it generic:

function sumOf<T>(array: T[]): T;

Keep in mind that you can't add a number and a bigint. You'll have to explicitly convert or get a runtime error.

[LionC]

As the type is determined by the selector, you could probably use

S extends (el: T) => number | (el: T) => bigint

as the type for selector and ReturnType<S> as the return type for the whole function.

The only problem is the empty input case - it needs to return 0 but you cannot know if that is bigint or number 0...

[grian32]

I don't think I'll be implementing bigint support in this PR as I don't know how to implement it type wise and the actual implementation would be scuffed enough that it'd just be wasteful in terms of memory and performance. @LionC @caspervonb But other than that I think it's good to go

[kt3k]

@grian32 LGTM. I think this is enough for the first pass. Thank you for your contribution!

[kt3k]

With regard to bigint support, how about providing explicit option or alternative function?

sumOf(arr, func, { bigInt: true });
sumOfBigInt(arr, func);

[LionC]

With regard to bigint support, how about providing explicit option or alternative function?

sumOf(arr, func, { bigInt: true });

sumOfBigInt(arr, func);

I think this is actually the only way to do this with the current signature - I do not see how we can decide which 0 to return for an empty input array.

That is something for another day then :-) Thank you a lot @grian32 , good work!