On 26 September 2011 16:25, Twan van Laarhoven
Hello list,
Currently the 'state' function is only defined for the State type (aka StateT Identity):
state :: (s -> (a, s)) -> State s a state f = StateT (Identity . f)
But this function makes sense for all MonadState instances. I therefore propose to either add it to the MonadState class:
class MonadState s m | m -> s where ... state :: (s -> (a,s)) -> m a state f = do s <- get let (a,s') = f s set s' return a
or as a stand alone function like modify. I personally prefer to add it to the class, since that allows for a more efficient implementation. In particular:
instance Monad m => MonadState s (StateT s m) where .... state = StateT (return . f)
Discussion period: 2 weeks (ends October 10th)
Twan
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+1 What happend to this proposal? Edward, could you also list yourself as maintainer of mtl and list the repository in the cabal file[1]? Cheers, Bas [1] http://www.haskell.org/cabal/users-guide/#source-repositories