Deepseq proposed patch

Julian Blake Kongslie jblake at
Thu Jun 10 17:15:05 EDT 2010

Henning Thielemann wrote:
> On Thu, 10 Jun 2010, Julian Blake Kongslie wrote:
>> instance (Data a) => NFData a where
>>  rnf a = dataDeepSeq a `seq` ()
> Is this an instance at all? It is not of the form NFData Type or NFData 
> (TypeCon a) or so.

Writing literally that instance would require the FlexibleInstances and 
UndecidableInstances extensions, I think, so you're right in that it's 
not a Haskell98 instance. The point of my email was more that I'm not 
sure it makes sense to have a "NFData" class, where "Data" would appear 
to suffice and be easier for programmers to work with.

I'm sending this reply to list; not sure what the standard for CCs is on 
this list.

-Julian Blake Kongslie
Please CC me on replies.

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