example.ex

  @spec new_grid(pos_int, pos_int) :: grid
  def new_grid(height, width), do: new_grid(height, width, [])

  @spec new_grid(pos_int, pos_int, [cell_state]) :: grid
  defp new_grid(h, w, acc)
  defp new_grid(0, _w, acc), do: acc
  defp new_grid(h, w, acc), do: new_grid(h - 1, w, [new_grid_line(w) | acc])

  @spec new_grid_line(pos_int, [cell_state]) :: [cell_state]
  defp new_grid_line(width, acc \\ [])
  defp new_grid_line(0, acc), do: acc
  defp new_grid_line(width, acc) do
    rand_state = Enum.random([:alive, :dead])
    new_grid_line(width - 1, [rand_state | acc])
  end