Kata 8/25 DLL

class Color
  attr_reader :color, :previous, :next

  def initialize(color)
    @color = color
    @previous = nil
    @next = nil
  end

  def link_to(color)
    @next = color
    color.link_from(self) if color.previous != self
    color
  end

  def link_from(color)
    @previous = color
    color.link_to(self) if color.next != self
    color
  end
end