Enumerable


 class MyEnum
   include Enumerable
   def initialize(*args)
     @values = args
   end
   def each
     @args.each{|x| yield x}
   end
 end

 e = MyEnum.new(1,2,3)
 e.reject{|x| x%2==0}  #=> [1,3]
 e.max                 #=> 3