first_out.clj

(defn first-out [& fns]
  (let [fs (atom [])
        ret (promise)
        terminate (fn [x] (println "cancling.." ) (doall (map future-cancel @fs)) (deliver ret x))]
    (reset! fs (doall
                (map (fn [x] (future-call #(terminate (x)))) fns )))
    @ret
    ))
 
(defn wait-for [n s]
  "this time, return the value"
  (fn [] (print "start...") (flush) (Thread/sleep n) (print s) (flush) s))
 
(first-out (wait-for 1000 "long") (wait-for 500 "short"))