Ashley Yakeley ashley at semantic.org
Sat Sep 2 01:28:36 EDT 2006

In article <20060901102733.GF21467 at iai.uni-bonn.de>,
 Andres Loeh <loeh at iai.uni-bonn.de> wrote:

> I think the stress here is on *new* extensions. I agree that an open
> type of type representations might be a more beautiful solution to the
> problem that Typeable solves. Nevertheless, the fact is that Simon's
> solution can be used in current GHC without further implementation work.

OK, fair enough. Open datatypes and functions will not, as you point 
out, be in Haskell'.

I'd also like to query O'Haskell here. Simon writes in the paper:

> O'Haskell extends Haskell with object-oriented subtyping.
> As such, it would be entirely possible to implement extensible
> exceptions using inheritance in O'Haskell.

I believe O'Haskell (like OOHaskell) doesn't provide the required 
dynamic downcasting operation either. AFAICT the extensions are 
essentially syntactic sugar: the subtyping is strictly static.

Ashley Yakeley, Seattle WA

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