If it's easy I think just generating the code and let the type checker
report any problems would be a great thing for standalone deriving.
-- Lennart
On Tue, Apr 14, 2009 at 10:10 AM, Simon Peyton-Jones
Yes, indeed, see http://hackage.haskell.org/trac/ghc/ticket/3012
Incidentally, the main Haskell list isn't the right place for GHC-specific questions. glasgow-haskell-users@haskell.org is the place
Simon
| -----Original Message----- | From: haskell-bounces@haskell.org [mailto:haskell-bounces@haskell.org] On Behalf Of | Norman Ramsey | Sent: 14 April 2009 05:28 | To: haskell@haskell.org | Subject: [Haskell] deriving Show for GADT? | | I've got a fairly large GADT for which I wished to use | deriving (Show) | but I got a mysterious error message: | | Exp.hs:13:11: | Can't make a derived instance of `Show (Exp a)' | (`Exp' has non-Haskell-98 constructor(s)) | In the data type declaration for `Exp' | | | This is from GHC. Does anybody know a compiler option or other trick | that will coax the compiler into producing a Show instance. | (I know I can write one by hand, but I'd rather not bother.) | | | Norman | _______________________________________________ | Haskell mailing list | Haskell@haskell.org | http://www.haskell.org/mailman/listinfo/haskell
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