Hello all,
Looking at the OOHaskell black (grey?) magic, and wondering if there
would be an interesting way to construct class interfaces using the
OOHaskell paradigm?
I'm trying to do it as so (assume relevant types/proxies declared):
type FigureInter = Record ( Draw :=: IO ()
:*: HNil
)
figure self = do
return emptyRecord
where
_ = narrow self :: FigureInter
abstrFigure self = do
super <- figure self
visible <- newIORef True
returnIO
$ setVisible .=. (\b -> writeIORef visible b)
.*. isVisible .=. readIORef visible
.*. draw .=. return ()
.<. super
but ghci complains (you know how it likes to complain), with
Couldn't match expected type `Record t2'
against inferred type `F (Proxy Draw) (m ())'
In the second argument of `(.*.)', namely `draw .=. (return ())'
In the second argument of `(.*.)', namely
`(isVisible .=. (readIORef visible)) .*. (draw .=. (return ()))'
In the first argument of `(.<.)', namely
`(setVisible .=. (\ b -> writeIORef visible b))
.*.
((isVisible .=. (readIORef visible)) .*. (draw .=. (return ())))'
Anyone have any tips they care to share? :)
Scott
_______________________________________________
Haskell-Cafe mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/haskell-cafe
