PingPong in Elixir

pingpong.exs

defmodule PingPong do
  def ping(parent_pid) do
    receive do
      {_, _, 0} -> send parent_pid, :done
      {pid, :pong, n} ->
        IO.puts("ping: " <> Integer.to_string(n))
        send pid, {self(), :ping, n-1}
        ping parent_pid
    end
  end
  def pong(parent_pid) do
    receive do
      {_, _, 0} -> send parent_pid, :done
      {pid, :ping, n} ->
        IO.puts("pong: " <> Integer.to_string(n))
        send pid, {self(), :pong, n-1}
        pong parent_pid
    end
  end
  def start(count) do
    ping_pid = spawn(PingPong, :ping, [self()])
    pong_pid = spawn(PingPong, :pong, [self()])
    send ping_pid, {pong_pid, :pong, count}
    receive do
      :done -> IO.puts("Done")
    end
  end
end