static TreeSet<S> toCaseInsensitiveSet(Iterable<S> c) {
  if (isCISet(c)) ret (TreeSet) c;
  TreeSet<S> set = caseInsensitiveSet();
  addAll(set, c);
  ret set;
}

static TreeSet<S> toCaseInsensitiveSet(S... x) {
  TreeSet<S> set = caseInsensitiveSet();
  addAll(set, x);
  ret set;
}