Re: Changes to Typeable

On 13/02/12 18:16, Edward Kmett wrote:

You could probably get away with something like

data Proxy = Proxy a

class Typeable a where typeOfProxy :: Proxy a -> TypeRep

typeOf :: forall a. Typeable a => a -> TypeRep typeOf = typeOfProxy (Proxy :: Proxy a)

which being outside of the class won't contribute to the inference of 'a's kind.

This would let you retain the existing functionality.

Simon's version has this: typeOf :: forall a. Typeable a => a -> TypeRep typeOf x = typeRep (getType x) where getType :: a -> Proxy a getType _ = Proxy (your version is clearer, though) I'm assuming there's no significance behind your renaming of 'typeRep' to 'typeOfProxy'? Cheers, Simon

On Mon, Feb 13, 2012 at 8:33 AM, Simon Marlow mailto:marlowsd@gmail.com> wrote:

On 10/02/2012 16:03, Simon Peyton-Jones wrote:

Friends

The page describes an improved implementation of the Typeable class, making use of polymorphic kinds. Technically it is straightforward, but it represents a non-backward-compatible change to a widely used library, so we need to make a plan for the transition.

http://hackage.haskell.org/__trac/ghc/wiki/GhcKinds/__PolyTypeable http://hackage.haskell.org/trac/ghc/wiki/GhcKinds/PolyTypeable

Comments? You can fix typos or add issues directly in the wiki page, or discuss by email

I've no objections to the plan itself, except that typeOf itself seems useful, so is there any need to deprecate it?

Cheers,

Simon

_________________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.__org mailto:Glasgow-haskell-users@haskell.org http://www.haskell.org/__mailman/listinfo/glasgow-__haskell-users http://www.haskell.org/mailman/listinfo/glasgow-haskell-users