Re: [Haskell-cafe] What's the advantage of writing Haskell this way?

On Mon, May 30, 2011 at 9:01 AM, John Ky wrote:

instance Monoid (Stream a) where mempty = Chunks mempty mappend (Chunks xs) (Chunks ys) = Chunks (xs ++ ys) mappend _ _ = EOF

I guess, it shows my lack of experience in Haskell, but my question is, why is writing the code this way preferred over say writing it like this:

I don't care for the inconsistency in this example, using both mempty and (++). Your version is at least consistent, but I'd actually prefer to use mappend instead of (++) here, because it makes it clear that this isn't actually defining a "new" Monoid instance, just translating an existing instance for the constructor parameter to work for the surrounding data type. - C.