simple ruby LRU cache

lru.rb

class LRU
  attr_reader :content
  attr_accessor :max

  def initialize(max, hash={})
    @max = max
    @content = hash
  end

  def [](key)
    content[key] = content.delete(key) if content.has_key? key
  end
  alias_method :get, :[]

  def []=(key, value)
    content.delete key if content.has_key? key
    content.delete(content.first.first) if content.length == max
    content[key] = value
  end
  alias_method :set, :[]=
end

sample.rb

lru = LRU.new(2)

lru.set :a, :a
lru.set :b, :b
lru.set :a, :a
lru.get :b
lru.set :c, :c

puts lru.content