// f : ES -> Collection<ES>
static Set<ES> mapLike functionReturningList_transitiveHull_ciSet_es(O f, ES input, O... _) {
  Set<ES> seen = optPar seen(_, linkedCISet_es());
  exhaustIterator(repeatFunctionReturningList_iterator(f, input, paramsPlus(_, +seen)));
  ret seen;
}