await_futures   xtlang

;;
;; async returns a 'future' which will
;; block until a result is ready.
;;
(bind-func await_futures
  (lambda (num:i64)
    (letz ((future1 (async (lambda () ;; aysnc accepts zero arguments
                             (let ((ress 0))
                               (thread_sleep 5 0)
                               (doloop (i num) (set! ress (+ ress (* i i i))))
                              5))))
           (future2 (async (lambda (x) ;; async also optionally accepts one argument
                             (thread_sleep 2 0)
                             x)
                           10)) ;; must give async the argument to be applied!
           ;; (future3 (async (lambda () ;; AN INFINITE FUTURE!
           ;;                   (while (future3.running:i1)
           ;;                     (thread_sleep 1 0))
           ;;                   20)))
           (result 0))
      (println "\nCheck for finish")
      (doloop (i 11)
        ;; (if (> i 7) (async_kill future3)) ;; after 7 force kill future3
        (println "finished 1:" (async_done future1)
                 " finished 2:" (async_done future2))
                 ;" finished 3:" (async_done future3))
        (thread_sleep 1 0))
      ;; add the three futures!
      (set! result (+ (future1) (future2))) ; (future3)))
      (println "(future1) + (future2) =" result)
      result)))