`clojure.core/repeatedly`¶

Type: function Added: Clojure 1.0 Examples: 5 Runnable: 3

([f] [n f])

Takes a function of no args, presumably with side effects, and returns an infinite (or length n if supplied) lazy sequence of calls to it

Examples¶

by gstamp on 2010-07-14

by Jeff Rose on 2010-09-03

by Jjunior130 on 2017-01-07

by reborg on 2018-03-09 . May have evaluation errors.

;; "repeatedly" used to build a infinite sequence of side-effecting futures.
;; Futures are taken in batch of "parallel" concurrent threads. The queue
;; can be fed while the loop is running. "done?" determines the exit condition.

(import '[java.util.concurrent ConcurrentLinkedQueue])
(def q (ConcurrentLinkedQueue. (range 100)))

(let [parallel 5
      done? #(> (reduce + (remove nil? %)) 30)
      task #(do (println "start" %) (Thread/sleep 1000) (inc %))]
  (loop [workers (repeatedly
                   #(let [out *out*]
                      (future
                        (binding [*out* out]
                          (when-let [item (.poll q)]
                            (task item))))))]
    (println "-> starting" parallel "new workers")
    (let [futures (doall (take parallel workers))
          results (mapv deref futures)]
      (cond
        (done? results) results
        (.isEmpty q) (println "Empty.")
        :else (recur (drop parallel workers))))))

;; -> starting 5 new workers
;; startstart  03
;;
;; startstart  1
;; 2start 4
;;
;; -> starting 5 new workers
;; start 5start
;; start start7start
;;   6
;; 8
;;  9
[6 7 8 9 10]

by loeschzwerg on 2019-12-15 . May have evaluation errors.

Note by boxie¶

if the function you want to repeat doesn't have side effects and has an argument, 'iterate' may be what you are looking for.

clojure.core/repeatedly¶

Examples¶

Note by boxie¶

See also¶

`clojure.core/repeatedly`¶