static S clUnparse(Lisp l) {
  if (l == null) ret "";
  ret join(" ", concatLists(ll(conceptQuote(l.head), (L<S>) map(f clUnparse_sub, l)));
}

static S clUnparse_sub(Lisp l) {
  ret l.empty() ? clUnparse(l) : "(" + clUnparse(l) + ")";
}