Loom Lock

ppmap.clj

(defn ppmap
  [f coll]
  (->> coll
       (mapv
         (fn [x]
           (let [cf (java.util.concurrent.CompletableFuture.)]
             (Thread/startVirtualThread
               (bound-fn []
                 (try
                   (.complete cf (f x))
                   (catch Exception e
                     (.completeExceptionally cf e)))))
             cf)))
       (map deref)))

(let [n 4]
   (->> (range n)
        (ppmap
          (fn [_]
            (->> (range n)
                 (ppmap (fn [_]
                          (->> (range n)
                               (ppmap (fn [_]
                                        (ppmap identity (range n))))
                               (apply concat)
                               (into #{}))))
                 (apply concat)
                 (into #{}))))
        (apply concat)
        (into #{})))