// attractors: map of words (lower case) to number of changes allowed
static S levenAttract(Map<S, Int> attractors, S text) {
  L<S> tok = javaTok(text);
  for (int i = 1; i < l(tok); i += 2) {
    S t = tok.get(i);
    if (!startsWithLetter(t)) continue;
    tok.set(i, levenAttract_word(attractors, t));
  }
  ret join(tok);
}

static S levenAttract_word(Map<S, Int> attractors, S word) {
  word = toLower(word);
  if (attractors.containsKey(word)) ret word;
  S best = null;
  int bestScore = 1000;
  for (S attractor : keys(attractors)) {
    int limit = attractors.get(attractor);
    int diff = leven_limited(attractor, word, min(limit+1, bestScore));
    if (diff <= limit && diff < bestScore) {
      best = attractor;
      bestScore = diff;
    }
  }
  ret or(best, word);
}