Definition partially_filled(i n: Z)(f: Z -> int): list val := 
  (map Vint (fill_list i f)) ++ (repeat_op_table (n-i) Vundef id).

Lemma Znth_partially_filled: forall (i j n: Z) (f: Z -> int), 0 <= i -> i < j -> j <= n -> Znth i (partially_filled j n f) = Vint (f i).