Clojure function that evaluates long running functions and wait for all functions return.

wait-all.clj

(ns script
  (:require [clojure.core.async :as async]))

(defn long-computation 
  "simulate long running operation"
  [x]
  (Thread/sleep 1000)
  (rand-int x))


(defn wait-all 
  "wait-all takes sequence of long running functions and wait for all
  functions to complete, returns vector of values. 
  It does not wait sequentially which produces
  non-deterministic sequence."
  [fns] 
  (let [chans (map (fn [f] (async/go (f))) fns)
        fn-length (count fns)
        acc-chans (async/merge chans)]

    (loop [i fn-length result '()]
      (if (zero? i)
        result
        (recur (dec i) (cons (async/<!! acc-chans) result))))))



(time (wait-all 
        ; create 100 functions with 1s delay
        (repeat 100 (partial long-computation 10))))

; we managed to complete all functions and retrieve the values asynchronously
;=> "Elapsed time: 1004.285832 msecs"