On Sat, Aug 25, 2012 at 3:25 AM, Erik Hesselink wrote:

I'm not sure if you already have something working, but we have several in our codebase, all following a similar pattern. For example:

newtype GeoServer a = GeoServer { unGeoServer :: ReaderT GeoServerState (ServerPartT IO) a }

instance MonadBaseControl IO GeoServer where newtype StM GeoServer a = StMGeoServer { unStMGeoServer :: StM (ReaderT GeoServerState (ServerPartT IO)) a } liftBaseWith f = GeoServer (liftBaseWith (\run -> f (liftM StMGeoServer . run . unGeoServer))) restoreM = GeoServer . restoreM . unStMGeoServer

Thank you all, i've adapted Chris's code which is similar to yours, and it works now.

Erik

On Wed, Aug 22, 2012 at 9:16 AM, yi huang wrote:

...

I have a `newtype Yun a = Yun { unYun :: ReaderT YunEnv (ResourceT IO) a }` , and i need to define an instance of `MonadBaseControl IO` for it. Newtype instance deriving don't work here. I guess the answer is simple, i just can't figure it out, hope anybody can lightening me.

Best regards. Yihuang.

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