From: "Peña, Botp" <botp@...>
Date: 2007-08-21T12:33:45+09:00
Subject: Re: Detecting duplicates in an array, anything in the standard library ?

From: Thibaut Barr�re [mailto:thibaut.barrere@gmail.com] 
#     inject({}) {|h,v| h[v]=h[v].to_i+1; h}.reject{|k,v| v==1}.keys

sshhh, in ruby1.9, i think you just do 

   group_by{|e|e}.select{|_,v| v.size>1}.keys

yes, yes, hash#select now hopefully returns hash.
can't we have group_by now ?  :)

kind regards -botp