Ruby circular doubly-linked list http://sausheong.blogspot.com/2012/04/ruby-circular-doubly-linked-list.html

circular_list.rb

#https://github.com/bangthetable/CircularList/blob/master/lib/circular_list.rb
module CircularList
  class List
    def initialize(array)
      @arr = array
    end

    def size
      @arr.size
    end

    def fetch_previous(index=0)
      index.nil? ? nil : @arr.unshift(@arr.pop)[index]
    end

    def fetch_next(index=0)
      index.nil? ? nil : @arr.push(@arr.shift)[index]
    end
    
    def fetch_after(e)
      fetch_next(@arr.index(e))
    end
    
    def fetch_before(e)
      fetch_previous(@arr.index(e))
    end
  end
end

CircularList.rb

class CircularList < Array
  def index
    @index ||=0
    @index.abs 
  end
  
  def current
    @index ||= 0
    get_at(@index)
  end
  
  def next(num=1)
    @index ||= 0
    @index += num
    get_at(@index)
  end
  
  def previous(num=1)
    @index ||= 0
    @index -= num
    get_at(@index)
  end
  
  private
  def get_at(index)
    if index >= 0
      at(index % self.size)
    else
      index = self.size + index
      get_at(index)
    end
  end
  
end