Hello Alfonso, Friday, April 6, 2007, 9:33:45 PM, you wrote: > (I'm not that comfortable working with existentials yet :)). probably you may benefit from looking at http://haskell.org/haskellwiki/OOP_vs_type_classes and original Wadler's paper mentioned there -- Best regards, Bulat mailto:Bulat.Ziganshin at gmail.com