[Haskell] deriving Show for GADT?
nr at cs.tufts.edu
Tue Apr 14 00:28:20 EDT 2009
I've got a fairly large GADT for which I wished to use
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.)
More information about the Haskell