manifold-cancel.clj

(require '[manifold.deferred :as d])

(defn long-boring-computation []
  (let [result (d/deferred)]
    (d/future
      (dotimes [_ 100]
        (when-not (d/realized? result)
          ;; block the thread is still a bad idea :(
          (Thread/sleep 1e3)))
      (d/success! result "I'm done with this"))
    result)))
  
(def f1 (long-boring-computation))
;; we're already running

(d/error! f1 (Exception. "I don't need this, sorry"))
;; will stop on the next iteration