Stream.fromを無理やり使ったフィボナッチ数列

gistfile1.ml

open Core.Std

let rec fib () =
  let tmp = ref (0, 1) in
  let fib_next n =
    match !tmp with
    | (cur, next) -> begin
        tmp := (next, cur+next);
        Some cur
      end
  in
  Stream.from fib_next

let main () =
  let f = fib () in
  printf "%d\n" (Stream.next f);
  printf "%d\n" (Stream.next f);
  printf "%d\n" (Stream.next f);
  printf "%d\n" (Stream.next f);
  printf "%d\n" (Stream.next f);
  printf "%d\n" (Stream.next f)

let () = main ()