simple-interest-calc.ex

    def interest_calc(initial_amount, interest, monthly_addition, months) do
      Stream.unfold(initial_amount, fn x ->
        month_end_principle = x + monthly_addition
        new_principle = month_end_principle * (1 + (interest/12))
        {new_principle, new_principle}
      end) |> Enum.take(months)
    end