IMPLEMENTATION MODULE DOpaque;
(* Completes opaque Node here; clients never see the record. *)
TYPE Node = RECORD v : INTEGER END;
VAR head : NodePtr;
PROCEDURE Init : NodePtr;
BEGIN
  NEW(head);
  head^.v := 55;
  RETURN head
END Init;

PROCEDURE Value(p : NodePtr) : INTEGER;
BEGIN
  RETURN p^.v
END Value;

END DOpaque.