[Haskell-cafe] Can it be proven there are no intermediate "useful" type classes between Applicative Functors & Monads?
dmbarbour at gmail.com
Tue Jun 7 18:14:32 CEST 2011
On Sun, Jun 5, 2011 at 12:51 PM, KC <kc1956 at gmail.com> wrote:
> If new intermediate classes crop up then there would be no point in fixing
> class (Applicative m) => Monad m where
> since it would have to be changed if new intermediate classes are found.
You might check out a few articles regarding Kleisli arrows  for
possibilities that live between applicative and monad.
Applicative itself is also a little on the strong side. I had to reject
Applicative for one model of signal transformers because 'pure' was not a
legal constructor, even though 'fmap . const' and '<*>' were okay. And even
Functor is too strong if you want effective linearity. I've found Adam
Megacz's Generalized Arrows  to be a suitable chassis for weaker models.
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the Haskell-Cafe