Add filter, map and reduce to Array

[KoBeWi]

Closes #17268

Example code:

func _ready() -> void:
	var array = [1, 2, 3, 4, 5, 6, 7, 8]
	
	print(array.filter(filter_test))
	print(array.map(map_test))
	print(array.reduce(reduce_test))

func filter_test(element: int) -> bool:
	return element < 4

func map_test(element: int) -> String:
	return str("element ", element)

func reduce_test(accum: int, element: int) -> int:
	return accum + element

The result is:

[1, 2, 3]
[element 1, element 2, element 3, element 4, element 5, element 6, element 7, element 8]
36

EDIT:
Here's lambda version btw:

func _ready() -> void:
	var array = [1, 2, 3, 4, 5, 6, 7, 8]
	print(array.filter(func(i): return i < 4))
	print(array.map(func(i): return str("element ", i)))
	print(array.reduce(func(i, accum): return accum + i))

[KoBeWi]

Ok, added error checking (not sure if I did it correctly) and docs.

[mhilbrunner]

Docs look good to me

[EricEzaM]

If we are adding this, how about

Take(n) / TakeWhile(predicate)
Skip(n) / SkipWhile(predicate)
Any(predicate)
All(predicate)

Basically just implement part of C# linq lol.

Would be interested in working on that in a separate pr.

[Calinou]

@EricEzaM These can be implemented in a separate PR. Note that Any and All are also called some and every in other languages like JavaScript's Array.

[KoBeWi]

I done the requested changes. Also in another commit I optimized the filter method.

[vnen]

Sorry for taking so long, this slipped my mind. Although we need an okay from reduz to merge this.

[KoBeWi]

I pushed some changes. When doing the Tween PR I learned the proper way of handing Callable calls (by seeing how callv does it), so I changed the error handling. Should be more correct now.
(btw @vnen you still hold the "changes requested" status...)

[KoBeWi]

Rebased and updated documentation with lambda functions (also edited OP with lambda examples).

[vnen]

LGTM. Thanks!

[akien-mga]

Thanks!

[kleonc]

I see it's already merged but gonna write it in here anyway: docs descriptions for filter and map suggest these methods modify the original array. It should be explicitly stated that these methods return a new array with the results (and do not modify the original array they was called for). There's also a typo in reduce's docs.

[MikeSchulze]

very nice, thanks a lot