@Override
 public void send(EventHandler e) {
   e.startNonterminal(name, begin);
   int pos = begin;
   for (Symbol c : children) {
     if (pos < c.begin) e.whitespace(pos, c.begin);
     c.send(e);
     pos = c.end;
   }
   if (pos < end) e.whitespace(pos, end);
   e.endNonterminal(name, end);
 }