Re: [Haskell-cafe] Re: Applicative but not Monad

Am Samstag 31 Oktober 2009 12:25:17 schrieb Tom Davie:

On 10/31/09, Heinrich Apfelmus wrote:

...

The only possible monad instance would be

return x = Const mempty fmap f (Const b) = Const b join (Const b) = Const b

Your join doesn't seem to have the right type... Unless I'm missing something.

Bob

join (Const b :: Const b (Const b a)) = (Const b :: Const b a)