memoize_fn.clj

(defmacro memoize-fn [name args body]
  `(let [mem# (atom {})]
     (fn ~args
       (if-let [e# (find @mem# ~args)]
         (val e#)
         (let [ret# ~body]
           (swap! mem# assoc ~args ret#)
           ret#)))))

(->> (range 35)
     (map (memoize-fn fib [n]
                      (if (<= n 1)
                        n
                        (+ (fib (dec n)) (fib (- n 2))))))
     (dorun)
     (time))
; "Elapsed time: 1.672 msecs"