[Haskell] How to close a type class

Keean Schupke k.schupke at imperial.ac.uk
Fri Nov 12 07:57:13 EST 2004

Just spotted this typo:

> How can we prevent the user from adding instances to Fail, whilst 
> still exporting
> Fail so that it can be used in the constraints of other classes, like:
>     class MustBeInt a
>     instance MustBeInt a

    instance MustBeInt Int

>     instance Fail a => MustBeInt a


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