propp: 'concl' patterns;
assumptions: tactics for non-goal export;
use Display.pretty_thm_no_hyps;
assm vs. assume vs. presume;
tuned type goal;
tuned print_goal;
relative exports, absolute export_thm rule;
transfer_facts;
tuned;
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))"