Good idea! Simple, and I see no downsides. Pedro is putting in place a new Typeable library (using kind polymorphism) for GHC 7.8. Pedro, might you incorporate this? Simon | -----Original Message----- | From: libraries-bounces@haskell.org [mailto:libraries-bounces@haskell.org] On | Behalf Of Shachaf Ben-Kiki | Sent: 26 January 2013 04:07 | To: libraries@haskell.org | Subject: Proxy and new-typeable | | I see that the new-typeable branch in GHC is using "typeRep :: forall a. | Typeable a => Proxy a -> TypeRep" rather than "typeOf :: forall a. Typeable a | => a -> TypeRep". This is clearly a big improvement over using undefined | everywhere. | | I'd like to suggest a small change, if it hasn't been brought up before -- | "typeRep :: forall proxy a. Typeable a => proxy a -> TypeRep". This makes | typeRep compatible with any other Proxy type, since it doesn't use any | properties of the concrete type -- it just uses it to pass information about | the "a". Things that consume a Proxy don't ever need to refer to Proxy | explicitly. | | This would make Typeable compatible with other Proxy libraries, like the one in | "tagged". It would also make it compatible with any other type of kind * -> * | -- for example, "typeRep ([] :: [Int])" would be a valid, and arguable more | convenient, syntax for using typeRep. "Nothing :: Maybe Int" and so on would | work too. So things that produce a "proxy" don't need to refer to Proxy | explicitly either. | | Possibly this would make the Proxy type entirely unnecessary. If it stays, | though, I suggest that it belongs in a module other than Data.Typeable.Internal | -- it's a useful type for many other things, and as long as it's in base and | exposed to users, it might as well be treated as a type in its own right. It's | also a monad, can provide a variant of `asTypeOf`, and so on. | | Shachaf | | _______________________________________________ | Libraries mailing list | Libraries@haskell.org | http://www.haskell.org/mailman/listinfo/libraries