svoid test_CompactTreeSet() {
  LS list = repF(1000, () -> randomID(3));
  Set<S> set = asTreeSet(list);
  CompactTreeSet<S> cset = new(set);
  print(set);
  print(cset);
  assertEquals(asList(set), asList(cset));
  assertEqualsVerbose(l(set), l(cset));
  
  for (S a : shuffledIterator(list)) {
    set.remove(a);
    cset.remove(a);
    assertEquals(asList(set), asList(cset));
    assertEqualsVerbose(l(set), l(cset));
  }
}