Basic Binary Tree with test sample in Clojure

gistfile1.clj

;; binary tree using defrecord (as oppossed to maps)
(defrecord TreeNode [val l r])

;; constructor method: creates a new tree
(defn make-tree [root] 
  (TreeNode. root nil nil))

;; creates a new binary tree by appending v to existing tree
(defn tree-append [t v]
  (cond
    (nil? t)       (TreeNode. v nil nil)
    (< v (:val t)) (TreeNode. (:val t) (tree-append (:l t) v) (:r t))
    :else          (TreeNode. (:val t) (:l t) (tree-append (:r t) v))))

;; in-order traversal of binary tree
(defn traverse-in-order [t]
  (when t
    (concat (traverse-in-order (:l t)) [(:val t)] (traverse-in-order (:r t)))))

;; tests
(def sample-tree (make-tree 1))
(def sample-tree (reduce tree-append sample-tree [3 5 2 4 6]))  ;; show appending to new tree
(traverse-in-order sample-tree)   ;; show traversal
(traverse-in-order  (tree-append sample-tree 45))   ;; show traversing after appending