Interesting example. Yes, GHC builds recursive dictionaries these days. There's a bit of discussion in our SYB paper in ICFP'05. http://research.microsoft.com/%7Esimonpj/papers/hmap/ And Martin Sulzmann has a whole paper about this point. http://www.comp.nus.edu.sg/~sulzmann/ ("Co-induction...") Simon | -----Original Message----- | From: glasgow-haskell-users-bounces@haskell.org [mailto:glasgow-haskell-users- | bounces@haskell.org] On Behalf Of Ross Paterson | Sent: 12 December 2005 10:46 | To: glasgow-haskell-users@haskell.org | Subject: instance inference | | I'm puzzled that the following is accepted. Is some sort of greatest | fixed point computation used for instances? | | {-# OPTIONS_GHC -fglasgow-exts #-} | module M where | | class C a b where c :: a -> b -> Bool | | instance C b b => C (Maybe a) b where c x y = c y y | | f :: Maybe a -> Bool | f x = c x x | | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users@haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users