anchor.diff:        return result
       }
     | Univ n -> Success <| Univ n
  -  | Prim (str, tp) -> Success <| Prim (str, tp)
  +  | Postulated (str, tp) -> Success <| Postulated (str, tp)
   
   and apply (globals : Global.env) (t1 : term) (t2 : term) : term result =
     match t1 with
  
positive.code:   | Lambda (x, tp, tm) -> Lambda (x, shiftUp cutoff tp, shiftUp (S cutoff) tm)
    | App (t1, t2) -> App (shiftUp cutoff t1, shiftUp cutoff t2)
    | Univ n -> Univ n
    | Prim (str, tp) -> Prim (str, tp)
  
  
  
  
negative.code:       return t'
      }
    | Univ n -> Success <| Univ (S n)
    | Postulated (_, t) -> Success t
  