Look and Say in Elixir

look_and_say.ex

defmodule LookAndSay do
  @moduledoc """
  Documentation for LookAndSay.
  """

  def main(args) do
    number = hd args
    IO.puts(look_and_say(number))
  end

  @spec look_and_say(String.t) :: String.t
  def look_and_say(number) do
    number
    |> to_list_of_digits()
    |> to_list_of_count_tuples()
    |> Enum.reduce([], fn({count, digit}, acc) ->
      ["#{count}" <> digit | acc]
    end)
    |> Enum.join
  end

  defp to_list_of_digits(number) do
    number
    |> to_string
    |> String.graphemes
  end

  defp to_list_of_count_tuples(digits) do
    Enum.reduce(digits, [], fn(digit, acc) ->
      case acc do
        [{count, ^digit} | tl] -> [{count + 1, digit} | tl]
        acc -> [{1, digit} | acc]
      end
    end)
  end
end