Type wildcards, was: Re: [Haskell] GHC Error question

[Lennart Augustsson]

I should have said that the situation in H98 is quite bad.
There you can't make default instances.

On Dec 7, 2006, at 07:49 , Johannes Waldmann wrote:

> Lennart Augustsson wrote:
>
>> Speaking of wishlist, I'd also like to see context synonyms, e.g.,
>> context C a = (Ord a, Num a)
>>
>> The current situation is quite bad, there's no way to abstract
>> contexts.
>
> except by writing extra classes that encode the context,
> see for example class NFAC:
> http://141.57.11.163/cgi-bin/cvsweb/lib/Autolib/NFA/Data.hs.drift? 
> rev=1.16
>
> but this is of course only a hack, and it duplicates information
> since you have to repeat the context in  the default instance.
> At least this happens only in one place, so it is useful.
> -- 
> -- Johannes Waldmann -- Tel/Fax (0341) 3076 6479/80 --
> ---- http://www.imn.htwk-leipzig.de/~waldmann/ -------
>
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