fact: Fixpoint subset s1 s2 : bool := match s1, s2 with | Leaf, _ => true | Node _ _ _ _, Leaf => false | Node _ l1 x1 r1, Node _ l2 x2 r2 => match X.compare x1 x2 with | Eq => subset l1 l2 &&& subset r1 r2 | Lt => subsetl (subset l1) x1 l2 &&& subset r1 s2 | Gt => subsetr (subset r1) x1 r2 &&& subset l1 s2 end end.
imports: Orders OrdersFacts MSetInterface PeanoNat