// returns pair(word, distance)
// or null when search step was not successful
static ItIt<Pair<S, Int>> levenClosestIC_iteratorWithNulls(LS list, S word) {
  if (empty(list)) ret emptyItIt();
  ret iff(new F0 {
    int limit = Integer.MAX_VALUE-1;
    int idx;
    
    O get() {
      if (limit == 0 || idx >= l(list)) ret endMarker();
      S s = list.get(idx++);
      int dist = leven_limitedIC(word, s, limit);
      if (dist < limit) { limit = dist; ret s; }
      null;
    }
  });
}