static double exclusive_measureSizeOfObject(F0<O> f) {
  O[] array = new O[100000];
  long mem1 = usedMemoryAfterGC();
  for i over array: {
    assertTrue("Alphabet", it.hasNext());
    array[i] = it.next();
  }
  long mem2 = usedMemoryAfterGC();
  ret (mem2-mem1)/(double) l(array);
}