_but_ I don't like the $(xxx) syntax... Perhaps if Simon could be persuaded to allow deriving
clauses to be defined in TH?
data X x = X x $(deriveMyClass (reify X))
could perhaps be defined from
data X x = X x deriving MyClass
I saw the same suggestion earlier today on the Haskell list...
Keean.
Andre Pang wrote:
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:
http://www.haskell.org/th/papers.html
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