function INTVAL (VAL: MVL4_VECTOR)
    return INTEGER is
  variable SUM: INTEGER:= 0;
begin
  for  N in VAL'LOW to VAL'HIGH loop
    assert not(VAL(N) = 'X' or VAL(N) = 'Z')
    report "INTVAL inputs not 0 or 1"
    severity WARNING;
    if  VAL(N) = '1' then
      SUM := SUM + (2**N);
    end if;
  end loop;
  return SUM;
end INTVAL;
--Figure 3.28 Declaration of a function to convert type MVL4_VECTOR
 --to typeINTEGER