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

6 Mar 2009


      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