It compiles, but it doesn't work when i try to use it on lists. There
are some bugs in that code, but I need some time to fix it.
2008/3/21 Bas van Dijk <[EMAIL PROTECTED]>:
> 2008/3/21 Krzysztof Skrzętnicki <[EMAIL PROTECTED]>:
> > ...
>
> > I'd like to write the following code:
> >
> > instance (Ord a) => YOrd a where
> > ycmp x y = case x `compare` y of
> > LT -> (x,y)
> > GT -> (y,x)
> > EQ -> (x,y)
> >
> > But i get an error "Undecidable instances" for any type [a].
> > Does anyone know the way to solve this?
>
> The module compiles fine when you add the following pragma's to your module:
>
> {-# LANGUAGE FlexibleInstances #-}
> {-# LANGUAGE UndecidableInstances #-}
>
> See:
>
> http://www.haskell.org/ghc/docs/latest/html/users_guide/type-class-extensions.html#instance-rules
>
> http://www.haskell.org/ghc/docs/latest/html/users_guide/type-class-extensions.html#undecidable-instances
>
> regards,
>
> Bas
>
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