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