fact: Fixpoint subsetr (subset_r1 : tree -> bool) x1 s2 : bool := match s2 with | Leaf => false | Node _ l2 x2 r2 => match X.compare x1 x2 with | Eq => subset_r1 r2 | Lt => mem x1 l2 &&& subset_r1 s2 | Gt => subsetr subset_r1 x1 r2 end end.
imports: Orders OrdersFacts MSetInterface PeanoNat