Changes to Typeable

Ian Lynagh igloo at
Fri Feb 10 23:24:15 CET 2012

On Fri, Feb 10, 2012 at 04:03:42PM +0000, Simon Peyton-Jones wrote:
> 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. 

This sounds good, but what does it mean for other Haskell

I guess if they implement "deriving Typeable" then most code would
continue to work with the old Data.Typeable implementation (well, with
some small changes to handle things like the typeOf / typeRep change).

But it would be better if they could use the new definition. Is
PolyKinds sufficiently well-defined and simple that it is feasible for
other Haskell implementations to implement it?

By the way, shouldn't this be discussed on libraries@?


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