The latest, I think : GHC 7.0.1, mtl-2.0.1.0, base-4.3.0.0
2011/2/23 Daniel Fischer <[email protected]>: > On Wednesday 23 February 2011 09:58:56, Yves Parès wrote: >> I am using mtl-2. Importing Control.Monad.Error doesn't work, I have >> to explicitly import Control.Monad.Instances. > > Weird. Control.Monad.Error imports Control.Monad.Instances (), so it ought > to be visible. > What exact versions of mtl, base, GHC are you using? > >> >> 2011/2/22 Daniel Fischer <[email protected]>: >> > On Tuesday 22 February 2011 23:07:05, Yves Parès wrote: >> >> Hello, >> >> >> >> When importing Control.Monad.Error, it shows me that (Either e) is an >> >> instance of MonadFix, but not an instance of Monad. >> >> Isn't there a problem? >> > >> > Prelude Control.Monad.Error> :i Either >> > data Either a b = Left a | Right b -- Defined in Data.Either >> > instance (Eq a, Eq b) => Eq (Either a b) -- Defined in Data.Either >> > instance Monad (Either e) -- Defined in Control.Monad.Instances >> > instance Functor (Either a) -- Defined in Control.Monad.Instances >> > <snip> >> > instance MonadFix (Either e) -- Defined in Control.Monad.Fix >> > <snip> >> > >> > Works right here. With mtl-1.*, there's an (Error e) restriction on >> > the instances. > > _______________________________________________ Haskell-Cafe mailing list [email protected] http://www.haskell.org/mailman/listinfo/haskell-cafe
