ping-ponger.ex

defmodule PingPonger do
  def loop do
    receive do
      {:pong, sender} ->
        IO.puts("Pong!")
        send(sender, {:ping, self})
      {:ping, sender} ->
        IO.puts("Ping?")
        send(sender, {:pong, self})
      :exit ->
        IO.puts("Quitting")
      _ ->
        loop
    end

    loop
  end

  def ping(ponger) do
    send(ponger, {:ping, self})
  end

  def pong(pinger) do
    send(pinger, {:ping, self})
  end
end