PROCEDURE Trim(x: LONG; bias: LONG): LONG =
  (*
    Returns x - bias*SIGN(x), clipped at 0.
  *)
  BEGIN
    IF x > bias THEN 
      RETURN x - bias
    ELSIF x < -bias THEN
      RETURN x + bias
    ELSE
      RETURN 0.0d0
    END
  END Trim;