[Haskell-cafe] Re: Interesting problem from Bird (4.2.13)

[Gleb Alexeyev]

Gleb Alexeyev wrote:
> instance Eq a => Eq (CatList a) where
>     a == b = case (viewCL a, viewCL b) of
>                (Just (x, xs), Just (y, ys)) -> x==y && xs == ys
>                (Nothing, Nothing)           -> True
>                _                            -> False
I just realized that my solution is needlessly verbose, the following 
instance suffices:
 > instance Eq a => Eq (CatList a) where
 >     a == b = viewCL a == viewCL b