LSD - Lab 10 [OK]

type state = In | Out | MaybeIn | MaybeIn2 | MaybeIn3 | MaybeOut | MaybeOut2

let delta = function        (* function: state -> char -> state *)
  | In -> (function
             | '-' -> MaybeOut
             | _ -> In)
  | MaybeOut -> (function
    | '-' -> MaybeOut2
    | _ -> In)
  | MaybeOut2 -> (function
    | '>' -> Out
    | _ -> In)
  | Out -> (function
             | '<' -> MaybeIn
             | _ -> Out)
  | MaybeIn -> (function
             | '!' -> MaybeIn2
         | '<' -> MaybeIn
         | _ -> Out)
  | MaybeIn2 -> (function
    | '-' -> MaybeIn3
    | _ -> Out)
  | MaybeIn3 -> (function
    | '-' -> In
    | _ -> Out)

let fold_in f =                (* fold f on a character stream with initial value v *)
  let rec fold1 v =        (* that is, compute f (f (f (v c1) c2) c3 ...*)
    (try let c = input_char stdin in
        fun () -> fold1 (f v c)
     with _ -> fun () -> v) ()
  in fold1

  let _ = let rez = fold_in delta Out in prerr_endline (if rez <> Out && rez <> MaybeOut && rez<>MaybeOut2 then "ends in comment" else "OK")