Util.ml

module IntMap = Map.Make(struct type t = int let compare = compare end)

let hello () =
  let input = [1;2;3;4;4;5;100;100;1;2] in
  let counts =
    List.fold_left (fun map n -> IntMap.update n (
        function
        | None -> Some 1
        | Some c -> Some (c + 1)
      ) map)
    IntMap.empty
    input
  in
  counts
  |> IntMap.bindings
  |> List.iter (fun (key, count) -> Printf.printf "[%d] = %d\n" key count)