Splitting a list of items into two lists of odd and even indexed items

Question

I would like to make a function that accepts a list and returns two lists: the first contains every odd item, and the second contains every even item.

For example, g

Answer 1

It looks like this is what you were going for, which is indeed a nice way to do it as it's tail-recursive.

let splitList items =
  let rec splitOdd odds evens = function
    | [] -> odds, evens
    | h::t -> splitEven (h::odds) evens t
  and splitEven odds evens = function
    | [] -> odds, evens
    | h::t -> splitOdd odds (h::evens) t
  let odds, evens = splitOdd [] [] items
  List.rev odds, List.rev evens