[Haskell-cafe] Can it be proven there are no intermediate "useful" type classes between Applicative Functors & Monads?

[Ben Lippmeier]

On 06/06/2011, at 5:51 , KC 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.
> 
> I realize non-existence proofs are hard.

Not as hard as formalising "useful".

Ben.