Andre Pang ozone at
Wed Oct 13 10:50:06 EDT 2004

On 13/10/2004, at 10:02 AM, MR K P SCHUPKE wrote:

> Okay, I see the Generic type class stuff does not support multi
> parameter type classes. I guess I am stuck - any suggestions as to
> how best do this?
> I wish to be able to derive type level labels for datatypes, like
> the following:
> data Fred a = Fred a deriving TTypeable
> generates the instance:
> instance TTypeable a al => TTypeable (Fred a) (NCons (N3 (N4 (N5 
> Nil))) (TCons al Nil))

If you are happy to live on the edge a bit (which you seem to be happy 
with, considering that you're playing with GHC CVS ;), Template Haskell 
might be one way to do it.  See "Template Haskell: A Report from the 
Field", a paper where Ian Lynagh does exactly what you're trying to do:

% Andre Pang :

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