Recursive solution to http://elixirexperience.com/problems/2

p2.ex

defmodule P2 do

  def num_to_list(mx) when mx > 1 do
    num_to_list(mx, mx - 1)
  end

  def num_to_list(mx) do
    "#{mx}"
  end

  defp num_to_list(n, mx) when mx > 1 do
    num_to_list("#{mx},#{n}", mx - 1)
  end

  defp num_to_list(n, mx) do
    "#{mx},#{n}"
  end

end