[Haskell] Re: [Haskell-cafe] ANNOUNCE: Generic Haskell 1.80 (Emerald)

[Brandon S. Allbery KF8NH]

On Apr 12, 2008, at 13:33 , Thomas van Noort wrote:
>> On 12/04/2008, Thomas van Noort <thomas at cs.ru.nl> wrote:
>>
>>> That's a good question. Unfortunately, only Haskell98 types are
>>> currently
>>>  supported by the Generic Haskell compiler.
>>
>> I thought constrained types were Haskell 98, but now I'm in doubt...
>
> language. Generic Haskell is fully reflexive with respect to the types
> that are definable in Haskell 98, except for constraints in data-type
> definitions. So a data type of the form
>
> data Eq a => Set a = NilSet | ConsSet a (Set a)
>
> is not dealt with correctly. However, constrained data types are a  
> corner
> case in Haskell and can easily be simulated using other means.

I was under the impression "corner case" here means that H98 lets you  
write it but doesn't handle it very sanely (a GHC-specific extension  
being needed to achieve that).

-- 
brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery at kf8nh.com
system administrator [openafs,heimdal,too many hats] allbery at ece.cmu.edu
electrical and computer engineering, carnegie mellon university    KF8NH