static <S> Set<S> filterCISet(Iterable<S> c, O pred) {
  Set<S> x = ciSet();
  if (c != null) for (O o : c)
    if (isTrue(callF(pred, o)))
      x.add(o);
  ret x;
}

static L filterCISet(O pred, Iterable c) {
  ret filterCISet(c, pred);
}