static class Q implements AutoCloseable {
  S name = "Unnamed Queue";
  L<Runnable> q = synchroLinkedList();
  new SingleThread st;
  BlockingQueue<Runnable> q = new LinkedBlockingQueue;
  volatile bool retired;
  
  *() {}
  *(S *name) {}
  
  void add(Runnable r) {
    q.add(r);
    st.go(r { _run() });
  }
  
  void add(O r) {
    add(toRunnable(r));
  }
  
  void _run() {
    L<Runnable> l = cloneAndClearList(q);
    for (Runnable r : l) {
      if (!licensed() || retired) ret;
      pcall { r.run(); }
    }
  }
  
  // end after current items have been processed
  void done() {
    add(r { throw new Done; });
  }
  
  public void close() { retired = true; } // TODO: interrupt thread
  
  bool isEmpty() { ret q.isEmpty(); }
}