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;
NatSum = Main +
consts sum :: nat => nat
primrec
"sum 0 = 0"
"sum (Suc n) = Suc n + sum n"
end