// returns ranges from C to N
static L<IntRange> fullPhraseCache_tokenRanges(FullPhraseCache cache, LS tok) {
  new L<IntRange> out;
  if (cache == null) ret out;
  for (int i = 1; i < l(tok); i += 2) {
    int j = fullPhraseCache_longestPhraseLength(cache, tok, i);
    if (j > i) {
      out.add(IntRange(i, j-1));
      i = j;
    }
  }
  ret out;
}