Simple Ruby Queue

queue.rb

class MyQ
  def initialize
    @head = @tail = []
  end

  def enq(obj)
    @tail << obj << [] # must use methods that mutate the array here
    @tail = @tail[1]
    obj
  end

  def deq
    raise "queue is empty" if empty?
    obj = @head[0]
    @head = @head[1]
    obj
  end

  def empty?
    @head.empty? # @head == @tail would be slower
  end
end