From: Daniel DeLorme <dan-ml@...42.com>
Date: 2007-06-22T09:04:04+09:00
Subject: Re: Behaviour of Enumerables reject vs. select mixed into Hash

Trans wrote:
>   module Enumerable
>     def select(&blk)
>       o = self.class.new
>       each{|*e| o << e if blk[*e]}
>     end
>   end
> 
>   class Hash
>     def <<(e)
>       self[e[0]] = e[1]
>     end
>   end
> 
> The downside here is, it is less efficient and breaks backward
> compatibility.

Why the compatibility breakage? The same could be implemented to be 
fully backwards compatible:

    module Enumerable
      def select(&blk)
        o = respond_to?(:<<) ? self.class.new : Array.new
        each{|*e| o << e if blk[*e]}
      end
    end


Daniel