fact: Definition lbal l k r := match l with | Rd (Rd a x b) y c => Rd (Bk a x b) y (Bk c k r) | Rd a x (Rd b y c) => Rd (Bk a x b) y (Bk c k r) | _ => Bk l k r end.
imports: Bool List BinPos Pnat Setoid SetoidList PeanoNat