ruby methods that either yield or return Enumerator

Question

in recent versions of Ruby, many methods in Enumerable return an Enumerator when they are called without a block:

[1,2,3,4].map 
#=>         


        

Answer 1

Another approach might be:

class Array
    def double(&block)
        map {|y| y*2 }.each(&block)
    end
 end