// tok = CNC
static int matchStartUsingWordTree(L<S> tok, Map<S, O> tree) {
  S best = null; // best replacement found
  int bestIndex = 0; // till where to replace
  
  while true {
    if (j > 0) { // no default in root!
      S def = cast tree.get("<default>");
      if (def != null) {
        best = def; bestIndex = j;
        //print("best solution: " + sfu(bestSolution));
      }
    }
   
    if (j >= l(tok)) break;
    
    O t = tree.get(tok.get(j));
    if (translateUsingWordTreeC_debug)
      print(i + "-" + j + " / " + joinWithSpace(subList(tok, i, j+1)) + " => " + sfu(t));
    if (t == null) break;
    if (t instanceof S) {
      int k = j+1;
      if (translateUsingWordTreeC_printReplacements)
        print("translateUsingWordTreeC: replacing " + sfu(subList(tok, i, k-1) + " with " + quote(t));
      replaceTokens(tok, i, k, (S) t);
      ret k;
    }
    tree = (Map) t;
    j++;
  }
}