Old code broken by new Typeable class

[Carter Schonwald]

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 <allbery.b at gmail.com> wrote:

> On Tue, Aug 5, 2014 at 1:47 PM, Volker Wysk <verteiler at 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.
>>
>
> 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-alone-deriving
>
> --
> brandon s allbery kf8nh                               sine nomine
> associates
> allbery.b at gmail.com
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