a simple two stack based queue in ruby

double_stack.rb

class DoubleStack
  attr_accessor :inbox, :outbox
  def initialize
    @inbox = []
    @outbox = []
  end

  def enqueue(item)
    @inbox << item
  end

  def dequeue
    transfer if @outbox.empty?
    @outbox.pop
  end

  def front
    transfer if @outbox.empty?
    @outbox.last
  end

  private

  def transfer
    (1..@inbox.length).each { @outbox << @inbox.pop }
  end
end