class CD
include Comparable
@@plays = 0
attr_reader :name, :artist, :duration
attr_writer :duration
def initialize(name, artist, duration)
@name = name
@artist = artist
@duration = duration
@plays = 0 end
def to_s
"CD: #@name--#@artist (#@duration)" end
def <=>(other)
self.duration <=> other.duration end end