timek.clj

(def ^:dynamic *times* nil)

(defmacro timek
  "Evaluates expr and prints the time it took.  Returns the value of
 expr."
  {:added "1.0"}
  [k expr]
  (let [plus (fn [val val2] (if val (+ val val2) val2))]
    `(let [start# (. System (nanoTime))
           ret# ~expr
           t# (/ (double (- (. System (nanoTime)) start#)) 1000000.0)]
       (swap! *times* update-in [~k] ~plus t#)
       ret#)))

(defmacro with-timek
  [& body]
  `(binding [*times* (atom {})]
     ~@body
     (clojure.pprint/pprint @*times*)))