[Haskell-cafe] Some help needed to start Haskell with Yi

Henning Thielemann lemming at henning-thielemann.de
Wed Nov 18 21:03:09 EST 2009

Daniel Fischer schrieb:
> Am Donnerstag 19 November 2009 01:07:37 schrieb Henning Thielemann:
>> Seems to be that the author defined an orphan instance - something one
>> should never do!
> So what do you do if you need an instance ClassX TypeY but the author of the package that 
> defines TypeY hasn't provided one?

The author (me) has added the instance after it became aware to him (me) ...

> You can define an orphan instance or duplicate packageY but with the instance. Both are 
> bad. Providing an orphan instance until packageY has one seems the lesser evil to me.
> Are there any good options?

A separate package for that orphan instance would be the best solution.

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