fact: Fixpoint modus_run (i:nat) (b:mopair) (u :order term) (f : term -> bool) {struct i} : mopair := match i with O => b | S j => let c := modus_run j b u f in triage (modus_output_list (imp_list c) u) (filter_or f (already_said u)) (mop (nil term) (stat_ord c)) end.