(* Finite Automaton accepting binary words with two ones *)

datatype B 
  = Epsilon
  | One of B
  | Zero of B

fun D Epsilon = false
  | D (Zero R) = D R
  | D (One R) = D R

fun A Epsilon = false
  | A (Zero R) = A R
  | A (One R) = B R

and B Epsilon = false
  | B (Zero R) = B R
  | B (One R) = C R

and C Epsilon = true
  | C (Zero R) = C R
  | C (One R) =  D R


(* Examples *)

val resultat1 = A (One (One (Zero (Zero (Zero Epsilon)))))
val resultat1 = A (One (One (Zero (Zero (One Epsilon)))))