sclass LCLongerProds {
  LS literals;
  new TreeMap<Int, L<Int>> productions;
  Map<S, L<Int>> files;
  
  S itemToString(int idx) {
    new StringBuilder buf;
    itemToString_step(buf, idx);
    ret str(buf);
  }
  
  void itemToString_step(StringBuilder buf, int idx) {
    if (idx < l(literals))
      buf.append(literals.get(idx));
    else for (int i : productions.get(idx))
      itemToString_step(buf, i);
  }
}