James Edward Gray II <james / grayproductions.net> wrote: > > The Set class has this feature and I even like the name: > > irb(main):001:0> require "set" > => true > irb(main):002:0> langs = Set.new([:perl, :python, :ruby]) > => #<Set: {:perl, :python, :ruby}> > irb(main):003:0> langs.classify { |m| m.to_s[0, 1] } > => {"p"=>#<Set: {:perl, :python}>, "r"=>#<Set: {:ruby}>} That *is* nice - wonder if there'd be any issues with moving it into Enumerable. martin