exercism_bob.exs

defmodule Bob do
  def hey(input) do
    cond do
        String.strip(input) == ""      -> "Fine. Be that way!"
        String.ends_with?(input, "?")  -> "Sure."
        all_letters_uppercase?(input)  -> "Whoa, chill out!"
        true                           -> "Whatever."
    end
  end

  defp all_letters_uppercase?(input) do
    String.upcase(input) == input
    && (String.downcase(input) != input)
  end
end