static S tok_bracketsToQuoted(S s) {
  L<S> tok = javaTok(s);
  new L<S> t;
  Map<Int, Int> map = getBracketMap(tok);
  for (int i = 0; i < l(tok); i++) {
    Int dest = map.get(i);
    if (dest != null) {
      t.add(quote(join(subList(tok, i+2, dest-1))));
      i = dest;
    } else
      t.add(tok.get(i));
  }
  ret join(t);
}