scope onUserUtterance_addHandler.

static Lock #lock = lock();
static TailFile #tailFile;
static L #handlers = synchroList();

// f : voidfunc(S) - gets only the utterance
static void onUserUtterance_addHandler(VF1<S> handler) {
  lock lock;
  handlers.add(handler);
  if (tailFile == null)
    tailFile = onUserUtterance(voidfunc(S s) { pcallFAll(handlers, s) });
}

end scope