aspects.clj

(defn before-advice [fun]
   (fn [original]
       (fn [& args] (apply original (apply fun args)))))

(defn after-advice [fun]
   (partial comp fun))

(defn around-advice [fun]
   (fn [original]
       (fun original)))

(defn weave [pointcut namespaces & advice]
  (let [advice (apply comp (reverse advice))]
    (doseq [join-point (filter pointcut (vals (mapcat ns-interns namespaces)))]
	(prn join-point (meta join-point))
        (alter-var-root join-point advice))))