Ulf Norell wrote: > I'm not sure what you're asking... Me neither probably. > , but it's possible to get > > my_read :: .. => Expr -> Term a > > Previously given code: > > >-- Give a GADT for representation types > >data R a where > > Rint :: R Int > > Rbool :: R Bool > > Rpair :: R a -> R b -> R (a,b)
Yeah, I especially liked Joost Visser's version which is pretty slick. I was just wondering if it was possible to accomplish the same task in a different way, using type classes instead of GADTs, which would seem to work in a more top-downish fashion, as opposed to bottom-upish. But I'm not an expert enough with type systems to know if the... Ambiguous type variable `b' in the constraint: `MyRead b' arising from use of `my_read' at gadt_wobbly.hs:65:28-36 Probable fix: add a type signature that fixes these type variable(s) ...problem was fixable by adding a type signature or grafting on some additional type machinery. Thanks, Greg Buchholz _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe