On 8 November 2014 13:42, Andreas Abel
I am a bit alert about this discussion because it seems that we have quite different ideas about how the AMP implementation should affect the base libraries.
1. Where can we see and discuss the proposed changes?
Not on https://www.haskell.org/haskellwiki/Functor-Applicative-Monad_Proposal
Not on https://ghc.haskell.org/trac/ghc/ticket/9586
2. Imho, the reasonable thing is to
rewrite all of F/A/M base functions such that they use the minimal F/A/M constraints.
This of course includes
liftM :: (Functor m) => (a -> b) -> m a -> m b liftM2 :: (Applicative m) => (a -> b -> c) -> m a -> m b -> m c
I don't think it's wise to rewrite _all_ functions. In particular liftM and ap shoudl stay as they are. Those are implementations of fmap and <*> using monadic bind and thus useful for writing instances like:
instance Functor T where fmap = liftM instance Applicative T where pure = return; (<*>) = ap instance Monad T where ...
Changing ap will break a lot of code.