Some tuning:
- finite now uses rev_append (tail recursive!) to append stopper, because @
needs to much stack space for large strings
- repeat is now tail recursive
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))"