static <A, B> L<B> lambdaMapLike lazyMap_bitSet(IF1<A, B> f, L<A> l) {

  ret lazyMap_bitSet((O) f, l);

}

static L lazyMap_bitSet(fO f, fL l) {

  ret new RandomAccessAbstractList {

    final int size = l(l);

    new BitSet bitSet;

    new L data;

    public int size() { ret size; }

    public O get(int i) {

      if (bitSet.get(i))

        ret data.get(i);

      bitSet.set(i);

      O o = callF(f, l.get(i));

      listPut(data, i, o);

      ret o;

    }

  };

}