Hi, Text.PrettyPrint.HughesPJ (the same applies to ghc/compiler/utils/Pretty.lhs) contains infixl 6 <> infixl 6 <+> infixl 5 $$, $+$ whereas my intuition says that infixr will give more efficient implementation. Is my intuition wrong? It seems to be supported by the definitions of hcat, hsep, vcat being defined in terms of foldr. We on #haskell are also confused by the changelog entry starting "Cured massive performance bug." and ending "I'm not satisfied that I've done the best possible job. I'll send you the code if you are interested.". It looks to me like the change was made and the original mail about the problem appended without being reread? Thanks Ian