[Haskell-cafe] How to implement instance of MonadBaseControl IO

[yi huang]

On Sat, Aug 25, 2012 at 3:25 AM, Erik Hesselink <hesselink at gmail.com> 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 <yi.codeplayer at gmail.com> 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.
> >
> > _______________________________________________
> > Haskell-Cafe mailing list
> > Haskell-Cafe at haskell.org
> > http://www.haskell.org/mailman/listinfo/haskell-cafe
> >
>



-- 
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