Decorate a function to know how many times is called

counted_fun.clj

(defn counted [f]
  (let [times (atom 0)]             ; thread safe counter
    (with-meta (fn [& args]
                 (swap! times inc)
                 (apply f args))
               {:times times})))    ; associated as metadata

(defn times-runned [f]
  @(:times (meta f)))

(comment

(def cinc (counted inc))
#'user/cinc
user=> (cinc 1)
2
user=> (cinc 1)
2
user=> (cinc 1)
2
user=> (times-runned cinc)

)