(with_import "./rb.kp"
(let (
    first empty
    _ (println first " contains? " 1 " ? " (contains? first 1))
    second (insert first 1)
    _ (println second " contains? " 1 " ? " (contains? second 1))
    third (insert second 2)
    _ (println third " contains? " 1 " ? " (contains? third 1))
    _ (println third " contains? " 2 " ? " (contains? third 2))
    fourth (insert third 3)
    _ (println fourth " contains? " 1 " ? " (contains? fourth 1))
    _ (println fourth " contains? " 2 " ? " (contains? fourth 2))
    _ (println fourth " contains? " 3 " ? " (contains? fourth 3))
    _ (println fourth " contains? " 4 " ? " (contains? fourth 4))
    fifth (delete fourth 1)
    _ (println fifth " contains? " 1 " ? " (contains? fifth 1))
    _ (println fifth " contains? " 2 " ? " (contains? fifth 2))
    _ (println fifth " contains? " 3 " ? " (contains? fifth 3))
    _ (println fifth " contains? " 4 " ? " (contains? fifth 4))
    sixth (delete fifth 3)
    _ (println sixth " contains? " 1 " ? " (contains? sixth 1))
    _ (println sixth " contains? " 2 " ? " (contains? sixth 2))
    _ (println sixth " contains? " 3 " ? " (contains? sixth 3))
    _ (println sixth " contains? " 4 " ? " (contains? sixth 4))
    seventh (delete sixth 2)
    _ (println seventh " contains? " 1 " ? " (contains? seventh 1))
    _ (println seventh " contains? " 2 " ? " (contains? seventh 2))
    _ (println seventh " contains? " 3 " ? " (contains? seventh 3))
    _ (println seventh " contains? " 4 " ? " (contains? seventh 4))
) nil))