static <A> L<A> collectInstances(Iterable i, Class<A> c) {
  new L l;
  if (i == null) ret l;
  c = primitiveToBoxedTypeOpt(c);
  for (O o : i)
    if (isInstance(c, o))
      l.add(o);
  ret l;
}

static <A> L<A> collectInstances(Class<A> c, Iterable i) {
  ret collectInstances(i, c);
}