static <A> L<A> sortedByScoreFunction_withoutZero(Iterable<A> l, IF1<A, Number> f) {
  new Map<A, Double> map;
  fOr (A a : l) {
    double score = toDouble(f.get(a));
    if (score != 0)
      map.put(a, score);
  }
  ret keysSortedByValueDesc(map);
}