(left-branch set)
(adjoin-set x (right-branch set)))))
+
+;;; key lookup
+(defn lookup [given-key set-of-records]
+ (cond (empty? set-of-records) false
+ (equal? given-key (key (first set-of-records))) (first set-of-records)
+ :else (lookup given-key (rest set-of-records))))
\ No newline at end of file