Cooler elixir stack: Now with push

server.ex

defmodule Stack.Server do
  use GenServer

  def handle_call(:pop, _from, stack) do
    [ head | tail] = stack
    { :reply, head, tail }
  end

  def handle_cast({:push, data_to_push}, stack) do
    { :noreply, [ data_to_push | stack ] }
  end
end

iex(35)> { :ok, pid } = GenServer.start_link(Stack.Server, [5, "cat", 9])
{:ok, #PID<0.146.0>}
iex(36)> clear
iex(37)> GenServer.call(pid, :pop)
5
iex(38)> GenServer.cast(pid, {:push, "dog"})
:ok
iex(39)> GenServer.call(pid, :pop)
"dog"