On 16 April 2013 15:56, Clark Gaebel <cgae...@uwaterloo.ca> wrote: > The monad my code is currently written in is: > > type MC = MCT Identity -- where MCT is the monad transformer version of it. > > I have two options for threading state through this: > > MCT (ST s) a > StateT s MC a > > The first option would work if I had some function with the signature > > MCT Identity a -> MCT (ST s) a > > but I know of no such function, and the second one would work if I had some > way of making StateT a member of PrimMonad. > > Can I see an example with 'lift'?
You should just be able to use lift to convert any PrimMonad action into your MCT-based monad as long as MCT is an instance of the MonadTrans class. i.e. if `foo :: (PrimMonad m) => m a' and MCT is an instance of MonadTrans, then you can do `lift foo :: (PrimMonad m) => MCT m a', or `lift (lift foo) :: (PrimMonad m) => MCT (StateT s m) a'. As another option, I have an as-yet-unreleased library to let you avoid having to do lift . lift for PrimMonad-based actions: http://hub.darcs.net/ivanm/monad-prim > > - Clark > > On Tuesday, April 16, 2013, Ivan Lazar Miljenovic wrote: >> >> On 16 April 2013 15:04, Clark Gaebel <cgae...@uwaterloo.ca> wrote: >> > Hi list! >> > >> > I want to use MVectors in a StateT monad transformer. >> > >> > How do I do that? StateT isn't a member of 'PrimMonad', and I have no >> > idea >> > how to make it one. >> >> You can use Control.Monad.Trans.lift to lift the PrimMonad operations >> to PrimMonad m => StateT s m >> >> > >> > Regards, >> > - Clark >> > >> > _______________________________________________ >> > Haskell-Cafe mailing list >> > Haskell-Cafe@haskell.org >> > http://www.haskell.org/mailman/listinfo/haskell-cafe >> > >> >> >> >> -- >> Ivan Lazar Miljenovic >> ivan.miljeno...@gmail.com >> http://IvanMiljenovic.wordpress.com -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com http://IvanMiljenovic.wordpress.com _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe