Removing the datatype declaration of "order" allows the standard General.order
to be used. Thus we can use Int.compare and String.compare instead of the
slower home-grown versions.
consts normal :: ifex => bool
primrec
"normal(CIF b) = True"
"normal(VIF x) = True"
"normal(IF b t e) = (normal t & normal e &
(case b of CIF b => True | VIF x => True | IF x y z => False))"