Add a sum() method to Array

[Burstwright]

I think it seems reasonable to have this built-in, since it's such a common task. The implementation's similar to min() and max(), so I placed it next to those in the code.

[AThousandShips]

This is easily achieved with reduce which is exactly what that is for, I don't think this is all that required, see godotengine/godot-proposals#3776

It creates a bit of bloat in the engine, if we add sum we also need to add product, etc.

[Burstwright]

True, but the example given in the docs, Array.reduce(func(accum, number): return accum + number), seems a bit verbose to me. In terms of future bloat, Python has a built-in sum(), but no product(), so I'm not sure that's an inevitable outcome.

I understand if this doesn't get merged, though. It's not hard to implement in GDScript, but it seemed common enough to warrant a method.

[phylor]

Especially for beginners sum() is way easier to understand and read then Array.reduce(func(accum, number): return accum + number). The latter needs quite some mental capacity to understand what it does.

Most other languages I work with have a builtin sum, so I'd really appreciate it if GDScript had it as well! 🙏

[AThousandShips]

I don't necessarily agree with that "it's good for beginners" is a good argument for adding a feature that can easily be achieved with existing functionally

[MewPurPur]

I think we should keep Array an all-purpose container for variants, not favoring summable types for any of its methods.

The linked proposal doesn't argue well. Their use case is "I need it" and "If I do it in GDScript it'll be slow" -_-. Also parallels with Python don't work here because this isn't about syntax; we have our own unique variants and most of them can't be summed together. Meanwhile, reduce() can perfectly replicate what sum() could do in a slightly longer line of code, and it also fulfills other use cases, such as finding min or max and using custom methods of summing or comparing.