RFC: replace List.enum and List.enumFrom with zipWithIndex

[kim-em]

Currently we have List.enum : List α → List (Nat × α), List.enumFrom : Nat → List α → List (Nat × α), and Array.zipWithIndex : Array α → Array (α × Nat).

My current intentions are to:

• rename List.enum to List.zipWithIndex
• swap the pair order for the List functions
• give both List and Array's zipWithIndex a default from : Nat := 0 argument that subsumes the functionality of enumFrom, and remove List.enumFrom.

[nomeata]

Not sure. I (as a Haskell user) expect the zipWith family to take a higher order function, and the zip family to return tuples. By that (IMHO useful convention) I could imagine renaming enum to zipIndex. But I'd be surprised if zipWithIndex would not be what it is right now.

I could imagine dropping enum if you want to simplify the API, or making it simp directly to zipWithIndex and the tuple constructor.

[nomeata]

Ah, but maybe worth cleaning up whether its called …Index or …Idx.