LetExp([
 TypeDec[
  (counter,
   NameTy(int))],
 VarDec(c,true,SOME(counter),
  IntExp(0)),
 FunctionDec[
  (knockKnock,[   ],
NONE,
   SeqExp[
    IfExp(
     OpExp(EqOp,
      VarExp(
       SimpleVar(c)),
      IntExp(0)),
     CallExp(print,[
      StringExp("Knock knock.
")]),
     IfExp(
      OpExp(EqOp,
       VarExp(
        SimpleVar(c)),
       IntExp(1)),
      CallExp(print,[
       StringExp("Who's there?
")]),
      IfExp(
       OpExp(EqOp,
        VarExp(
         SimpleVar(c)),
        IntExp(2)),
       CallExp(print,[
        StringExp("Little old lady.
")]),
       IfExp(
        OpExp(EqOp,
         VarExp(
          SimpleVar(c)),
         IntExp(3)),
        CallExp(print,[
         StringExp("Little old lady who?
")]),
        CallExp(print,[
         StringExp("I didn't know you could yodel!
")]))))),
    AssignExp(
     SimpleVar(c),
     OpExp(PlusOp,
      VarExp(
       SimpleVar(c)),
      IntExp(1))),
    IfExp(
     OpExp(GtOp,
      VarExp(
       SimpleVar(c)),
      IntExp(4)),
     AssignExp(
      SimpleVar(c),
      IntExp(0)))])]],
 SeqExp[
  CallExp(knockKnock,[]),
  CallExp(knockKnock,[]),
  CallExp(knockKnock,[]),
  CallExp(knockKnock,[]),
  CallExp(knockKnock,[])])