On Tue, 1 Oct 2013 02:21:13 -0500, John Lato <jwl...@gmail.com> wrote: > It's not a solution per se, but it seems to me that there's no need for the > Monad superclass constraint on MonadIO. If that were removed, we could > just have > > class LiftIO t where > liftIO :: IO a -> t a > > and it would Just Work.
One concern with this is that it's not exactly clear what the semantics are on LiftIO (is liftIO a >> liftIO b equal to liftIO (a >> b) or not?) and the interaction between LiftIO and Applicative/Monad would have to be some sort of ugly ad-hoc law like we have with Bounded/Enum etc. Furthermore, you might end up specifying a lot of ‘redundant’ constraints like (Monad m, LiftIO m) that way, just a thing to keep in mind. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
