static ItIt<Int> countIterator_exclusive_backwards(int a, int b) {
  ret new ItIt<Int>() {
    int i = a;
    
    public bool hasNext() { ret i > b; }
    public Int next() { ret i--; }
  };
}

static <A> ItIt<A> countIterator_exclusive_backwards(int a, int b, IF1<Int, A> f) {
  ret mapI_if1(f, countIterator_exclusive_backwards(a, b));
}