static F1<S, Bool> boolGuesserByWordAtIndex(Map<S, Bool> examples, final int wordIndex) {
  Map<S, Bool> map = mapKeys(examples, func(S s) { getWord(s, wordIndex) }, keys(examples));
  int diff = countValues(map, true)-countValues(map, false);
  print("diff=" + diff);
  final bool defaultValue = diff > 0;
  final Set<S> exceptions = new TreeSet(keysWithValue(map, !defaultValue));
  ret func(S s) -> Bool {
    defaultValue ^ contains(exceptions, getWord(s, wordIndex))
  };
}