From: Stefan Lang <perfectly.normal.hacker@...>
Date: 2008-03-08T05:33:58+09:00
Subject: Re: ActiveSupport Enumerable#sum should not use #size

2008/3/7, Trans <transfire@gmail.com>:
> ActiveSupport defines this for Enumerable#sum:
>
>   module Enumerable
>
>     def sum(identity = 0, &block)
>       return identity unless size > 0
>
>       if block_given?
>         map(&block).sum
>       else
>         inject { |sum, element| sum + element }
>       end
>     end
>
>   end
>
>  The use of #size shouldn't be used in an Enumerable method --since it
>  is not part of Enumerable's defined interface..... Ah, I was just
>  about to ask what anyone thought the fix to this is, but it occurs to
>  me that it might be:
>
>     def sum(identity = 0, &block)
>       if block_given?
>         map(&block).sum
>       else
>         inject { |sum, element| sum + element } || identity

inject takes the identity as first parameter:

    inject(identity) { |sum, element| sum + element }

and since they define Symbol#to_proc, this can even be

    inject(identity, &:+)

>       end
>     end
>
>  Look right?
>
>
>  T.

Stefan