[Haskell-cafe] Help using CGIT
rich.neswold at gmail.com
Wed Aug 22 21:34:53 EDT 2007
On 8/22/07, Ian Lynagh <igloo at earth.li> wrote:
> On Wed, Aug 22, 2007 at 01:27:00PM -0500, Rich Neswold wrote:
> > > newtype App a = App (ReaderT Connection (CGIT IO) a)
> > > deriving (Monad, MonadIO, MonadReader Connection)
> > Unfortunately, when another module tries to actually use the monad, I
> > get warnings about "No instance for (MonadCGI App)". I tried making an
> > instance:
> > > instance MonadCGI App where
> > > cgiAddHeader = ?
> > > cgiGet = ?
> You have three choices:
> Provide a single instance for App that does the whole thing:
> instance MonadCGI App where
> cgiAddHeader n v = App $ lift $ cgiAddHeader n v
> cgiGet x = App $ lift $ cgiGet x
> This one you would obviously have to change if you added a StateT.
Bingo! Method #3 works beautifully! I missed the
Thanks for your help!
JID: rich at neswold.homeunix.net
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