mtram.ml

$ ocaml -w A
        OCaml version 4.02.3                                                                                                                                    
# type 'a mtram = Mdone of 'a | Mbind : 'b mtram * ('b -> 'a mtram) -> 'a mtram;;
type 'a mtram = Mdone of 'a | Mbind : 'b mtram * ('b -> 'a mtram) -> 'a mtram
# let rec eval : 'a . 'a mtram -> 'a = function
  | Mdone x -> x
  | Mbind (Mdone b, b_am) -> eval (b_am b)
  | Mbind (Mbind (cm, c_bm), b_am) -> eval (Mbind (cm, fun c -> Mbind (c_bm c, b_am)));;
val eval : 'a mtram -> 'a = <fun>
# let return a = Mdone a;;
val return : 'a -> 'a mtram = <fun>
# let ( >>= ) mb b_ma = Mbind (mb, b_ma);;
val ( >>= ) : 'a mtram -> ('a -> 'b mtram) -> 'b mtram = <fun>
# let rec is_even = function 0 -> return true | n -> return (n - 1) >>= is_odd
  and is_odd = function 0 -> return false | n -> return (n - 1) >>= is_even;;
val is_even : int -> bool mtram = <fun>
val is_odd : int -> bool mtram = <fun>
# let is_sum_even a b =
  return a >>= is_even >>= fun res_a ->
  return b >>= is_even >>= fun res_b ->
  return (res_a = res_b);;
val is_sum_even : int -> int -> bool mtram = <fun>
# eval @@ is_sum_even 5 7;;
- : bool = true
# eval @@ is_sum_even 4 5;;
- : bool = false
#