list span in elixir

span.exs

defmodule MyList do

  def span(from, to), do: _span(from, to, [])

  defp _span(from, to, list) when from == to do
    list ++ [to]
  end

  defp _span(from, to, list) do
    list ++ [from | _span(from + 1, to, list) ]
  end

end