svoid <A> deepDoubleWordIndex_add(DoubleWordIndex<WithIntArray<A>> wordIndex, A id, S text) {
  MultiMap<S, Int> positions = ciMultiMap();
  for (IntRange r : wordIndex.wordRanges(text))
    positions.put(substring(text, r), r.start);
  for (S word, L<Int> indices : positions.asMap())
    wordIndex.addWord(new WithIntArray<A>(toIntArray(indices), id), word);
}