Take delta of two lists

delta_list.ex

  @spec delta_list(path(), list(), list()) :: [delta()]
  defp delta_list(path, as, bs) when length(as) != length(bs), do: delta_simple(path, as, bs)

  defp delta_list(path, as, bs) do
    as
    |> indexed_zip(bs)
    |> Enum.flat_map(fn {i, {a, b}} -> delta([i | path], a, b) end)
  end
  
  def indexed_zip(as, bs, i \\ 0)
  def indexed_zip([], [], _), do: []
  def indexed_zip([a | as], [], i), do: [{i, {a, nil}} | indexed_zip(as, [], i + 1)]
  def indexed_zip([], [b | bs], i), do: [{i, {nil, b}} | indexed_zip([], bs, i + 1)]
  def indexed_zip([a | as], [b | bs], i), do: [{i, {a, b}} | indexed_zip(as, bs, i + 1)]