Re: Old code broken by new Typeable class

thats what i meant. I meant you can't WRITE the body of a typeable in 7.8, you can derive though On Tue, Aug 5, 2014 at 1:59 PM, Brandon Allbery wrote:

On Tue, Aug 5, 2014 at 1:47 PM, Volker Wysk wrote:

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Am Dienstag, 5. August 2014, 12:46:23 schrieb Carter Schonwald:

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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.

Are you sure? There is a standalone deriving syntax.

deriving instance Typeable ProcessStatus

http://www.haskell.org/ghc/docs/latest/html/users_guide/deriving.html#stand-...

-- brandon s allbery kf8nh sine nomine associates allbery.b@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net

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