C

anonymous-gist.clj

(defn C [n]
  (cond
    (one? n) 1
    (even? n) (C (div n 2))
    :else (C (add1 (times 3 n)))))

(defn C* [n]
  (cond
    (= 1 n) 1
    (clojure.core/even? n) (C (quot n 2))
    :else (C (inc (* n 3)))))

(defn try-with-C [f upto]
  (map (fn [n]
         (try (f n)
              (catch Exception e "Exception")))
       (range 1 (inc upto))))

(comment
  ;; Wow!
  (time (try-with-C C 100)) ;; "Elapsed time: 0.072 msecs"
  (time (try-with-C C* 100)) ;; "Elapsed time: 0.069 msecs"
  )