Re: Proposal: Applicative => Monad: Call for consensus

Er, hi... On 5 Jan 2011, at 11:24, Bas van Dijk wrote:

On Wed, Jan 5, 2011 at 11:33 AM, Simon Marlow wrote:

...

Furthermore, we have some significant compatibility issues with Haskell 98/2010 code. I wouldn't be in favour of doing this unless we can retain Haskell 98/2010 compatibility somehow (e.g. with superclass defaults or class aliases).

It would indeed be really nice to have something like this:

{-# LANGUAGE DefaultInstances #-}

class Functor f where fmap :: (a → b) → f a → f b

class Functor f ⇒ Applicative f where pure :: a → f a (<*>) :: f (a → b) → f a → f b

instance Functor f where fmap f m = pure f <*> m

[..]

Now only someone has to implement it :-)

(ahem) cabal install she http://personal.cis.strath.ac.uk/~conor/pub/she/superclass.html [ducks and runs] Conor