(* Attempt to replicate a coq file *)
datatype instr
  = Const of bool
  | Goto of int

type prog = instr list

fun eclosure_aux p idx visited =
  let
    val inds = List.tabulate (length p, fn x=>x)
    val aug = ListPair.zip (inds, p)
  in
    case (List.nth (aug, idx)) of
      (i, x) => 
        (case x of
          Const _ => [i]     
        | Goto k =>
	    if List.exists (fn x => x=k) visited then [i]
            else i :: (eclosure_aux p k (i::visited)))
  end
fun eclosure p idx = eclosure_aux p idx []

val p1 = [
  Const true,     (* 0 *)
  Const false,    (* 1 *)
  Goto 4,         (* 2 *)
  Const true,     (* 3 *)
  Goto 1          (* 4 *)
]

val p2 = [
  Const true,     (* 0 *)
  Const false,    (* 1 *)
  Goto 4,         (* 2 *)
  Const true,     (* 3 *)
  Goto 2          (* 4 *)
]
	     
val v1 = eclosure p1 2
(* [2,4,1] : int list *)

val v2 = eclosure p2 2