If you can't change the definition you can use the syntax Björn Bringert
added back in 2006 or so for StandaloneDeriving.
Just turn on
{-# LANGUAGE StandaloneDeriving, DeriveDataTypeable #-}
and then you can use
deriving instance Typeable Foo
-Edward
On Tue, Aug 5, 2014 at 1:47 PM, Volker Wysk <vertei...@volker-wysk.de>
wrote:
> Am Dienstag, 5. August 2014, 12:46:23 schrieb Carter Schonwald:
> > i assume 7.6 and 7.8, if we're talking GHC rather than GCC :)
> >
> > in 7.8 you can't define userland typeable instances, you need only write
> > deriving (Typeable) and you're all set.
> > add some CPP to select the instances suitable
>
> So you need to be able to change the definition of the data type, in order
> to
> add deriving (Typeable). It's not possible to add a Typeable instance
> declaration later.
>
> When you can't change the definition, you're out of luck.
>
> Okay,
> V.W.
> _______________________________________________
> Glasgow-haskell-users mailing list
> Glasgow-haskell-users@haskell.org
> http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
>
_______________________________________________
Glasgow-haskell-users mailing list
Glasgow-haskell-users@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
