I'm trying to implement the "Advanced Example : Type-Level Quicksort" from HaskellWiki using type families instead of functional dependencies. My code is at [1]. I substituted all 'many to one' functional dependencies like xs ys -> zs by explicit type families, but I don't know how to replace 'many to many' dependencies by type families only, so I've used associated types. But for some unknown to me reason the typechecker hangs if I try to get listQuickSort type signature in ghci. So I have 2 questions: what is the correct replacement of FDs in this case and where is an error in my code? I assume that the correct replacement exists (though it may not be very pretty) because "type families and functional dependencies are equivalent in expressiveness" [2]. Regards, Vladimir [1] http://hpaste.org/fastcgi/hpaste.fcgi/view?id=29380#a29380 [2] http://www.mail-archive.com/haskell-cafe@haskell.org/msg54024.html