PROCEDURE Sum(READONLY a: ARRAY OF REFANY): REAL =
  VAR sum := 0.0;
  BEGIN
    FOR i := FIRST(a) TO LAST(a) DO
      TYPECASE a[i] OF
      | NULL => (* skip *)
      | REF INTEGER (e) => sum := sum + FLOAT(e^);
      | REF REAL(e) => sum := sum + e^;
      ELSE (* skip *)
      END;
    END;
    RETURN sum;
  END Sum;