// old syntax
static <A> L<A> filterListByPredicateOnIndex(O pred, L<A> l) {
  new L<A> out;
  int n = l(l);
  for i to n:
    if (isTrue_callF(pred, i))
      out.add(l.get(i));
  ret out;
}

static <A> L<A> lambdaMapLike filterListByPredicateOnIndex(IIntPred pred, L<A> l) {
  new L<A> out;
  int n = l(l);
  for i to n:
    if (pred.get(i))
      out.add(l.get(i));
  ret out;
}

static <A> L<A> filterListByPredicateOnIndex(L<A> l, IIntPred pred) {
  ret filterListByPredicateOnIndex(pred, l);
}