[Haskell] deriving Show for GADT?
ben_moseley at mac.com
Tue Apr 14 01:43:48 EDT 2009
Unfortunately, this isn't supported at present.
On 14 Apr 2009, at 05:28, Norman Ramsey wrote:
> I've got a fairly large GADT for which I wished to use
> deriving (Show)
> but I got a mysterious error message:
> 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.)
> Haskell mailing list
> Haskell at haskell.org
More information about the Haskell