binary.exs

defmodule Binary do

  def strip_vowels("", acc), do: acc
  def strip_vowels(<<head::binary-size(1), rest::binary>>, acc \\ "") do 
    strip_vowels(rest, acc <> check_vowels(head))
  end

  defp check_vowels("a"), do: ""
  defp check_vowels("e"), do: ""
  defp check_vowels("i"), do: ""
  defp check_vowels("o"), do: ""
  defp check_vowels("u"), do: ""
  defp check_vowels(letter), do: letter
end