Adding IdentityT to mtl

[Iavor Diatchki]

Hi,
I comlpletely forgot about this.  I have added two new transformers to
monadLib: IdT and LiftT, the second one using a strict bind.  These
changes are available in the darcs repository.  When I get around to
playing around with them a bit more I will make a new package and put
it on hackage.
-Iavor

On 8/28/07, Josef Svenningsson <josef.svenningsson at gmail.com> wrote:
> Whatever happened to the suggestion of extending mtl with IdentityT? I
> think it's reasonable, especially since we have a documented use case.
>
> /Josef
>
> On 6/1/07, Donald Bruce Stewart <dons at cse.unsw.edu.au> wrote:
> > I wanted an IdentityT today, for extending xmonad. (The idea is to
> > allower user-defined monad transformers, so users can plug in their own
> > semantics easily).
> >
> > By default it would use IdentityT, which I note is not in mtl!
> >
> > Here's roughly what it would be:
> >
> >     -----------------------------------------------------------------------------
> >     -- |
> >     -- Module      :  Identity.hs
> >     -- License     :  BSD3-style (see LICENSE)
> >     --
> >     module IdentityT where
> >
> >     import Control.Monad.Trans
> >
> >     --
> >     -- IdentityT , a parameterisable identity monad, with an inner monad
> >     -- The user's default monad transformer
> >     --
> >
> >     newtype IdentityT m a = IdentityT { runIdentityT :: m a }
> >
> >     instance (Functor m, Monad m) => Functor (IdentityT m) where
> >         fmap f = IdentityT . fmap f . runIdentityT
> >
> >     instance (Monad m) => Monad (IdentityT m) where
> >         return   = IdentityT . return
> >         m >>= k  = IdentityT $ runIdentityT . k =<< runIdentityT m
> >         fail msg = IdentityT $ fail msg
> >
> >     instance (MonadIO m) => MonadIO (IdentityT m) where
> >         liftIO = IdentityT . liftIO
> >
> > Any reasons why this shouldn't be in mtl?
> >
> > -- Don
> > _______________________________________________
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> >
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