Hi, I would like to add some minor improvement on usability of the existential type Connection proposed by Bulat. > data Connection = forall c . (IsConnection c) => Conn c The thing is that you usually have functions like send :: (isConnection c) => c -> String -> IO() or whatever. In order to be able to feed a variable of type Connection into functions like send it is handy to define
instance IsConnection Connection where
foo (Conn c) = foo c
setFoo bar (Conn c) = Conn $ setFoo bar c
...
which delegates functions "into" the item inside the exitential wrapper.
Cheers,
Georg
--
---- Georg Martius, Tel: (+49 34297) 89434 ----
------- http://www.flexman.homeip.net ---------
pgptjsuHVMKMf.pgp
Description: PGP signature
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
