Re: [Haskell-cafe] ANNOUNCE: monad-control-0.3

On Tue, Dec 6, 2011 at 11:49 AM, Bas van Dijk wrote:

On 6 December 2011 05:06, Michael Snoyman wrote:

...

Maybe this will help[1]. It's using RWST instead of StateT, but it's the same idea.

[1] https://github.com/yesodweb/yesod/commit/7619e4e9dd88c152d1e00b6fea073c3d52d...

Hi Michael,

Note that you can just reuse the MonadTransControl instance of the RWST transformer:

instance MonadTransControl (GGWidget master) where    newtype StT (GGWidget master) a =        StWidget {unStWidget :: StT (GWInner master) a}    liftWith f = GWidget $ liftWith $ \run ->                   f $ liftM StWidget . run . unGWidget    restoreT = GWidget . restoreT . liftM unStWidget

Cheers,

Bas

Thanks Bas, I was just in the process of converting Widget from being a RWS to a Writer, and your code made it much simpler :). Michael