static <A> L<A> joinStreaks(O filter, O joiner, L<A> l) {
  int start = 0;
  new L out;
  for (int i = 0; i < l(l); i++) {
    if (!isTrue(callF(filter, l.get(i)))) {
      if (i == start+1)
        out.add(l.get(start));
      else if (i > start)
        out.add(callF(joiner, subList(l, start, i)));
      start = i+1;
      out.add(l.get(i));
    }
  }
  if (start == l(l)-1)
    out.add(l.get(start));
  else if (l(l) > start)
    out.add(callF(joiner, subList(l, start)));
  ret out;
}