Understanding Clojure concurrency example
- by dusha
Hello,
I just go through various documentation on Clojure concurrency and came accross the example on the website (http://clojure.org/concurrent_programming).
(import '(java.util.concurrent Executors))
(defn test-stm [nitems nthreads niters]
(let [refs (map ref (replicate nitems 0))
pool (Executors/newFixedThreadPool nthreads)
tasks (map (fn [t]
(fn []
(dotimes [n niters]
(dosync
(doseq [r refs]
(alter r + 1 t))))))
(range nthreads))]
(doseq [future (.invokeAll pool tasks)]
(.get future))
(.shutdown pool)
(map deref refs)))
I understand what it does and how it works, but I don't get why the second anonymous function fn[] is needed?
Many thanks,
dusha.
P.S. Without this second fn [] I get NullPointerException.
