static <A extends Iterator<S>> ItIt<S> repeatedInputModificationsIterator(S input, final F1<S, L<A>> makeIterators) {

  final HashSet<S> seen = lithashset(input);

  // Make pool of iterators

  final new LinkedList<Iterator<S>> pool;

  addAll(pool, callF(makeIterators, input));

  ret iteratorFromFunction(func -> S {

    while ping (!empty(pool)) {

      Iterator<S> it = first(pool);

      if (!it.hasNext()) continue with removeFirst(pool);

      // Get entry and check if seen already

      S entry = it.next();

      if (!seen.add(entry)) continue;

      // found new entry - return and schedule for further analysis

      addAll(pool, callF(makeIterators, entry));

      ret entry;

    }

    null;

  });

}