Hi,
Consider I have declarations like this:
class (ClassA a) => ClassC a where
from :: (ClassB b) => a -> [b]
to :: (ClassB c) => a -> [c]
data H = ...
instance ClassB H where
...
data Test = Test { m :: H }
instance ClassA Test where
...
instance ClassC Test where
from = m
to = m
Well, I got "could not deduce" error here at "from = m" and "to =
m". `c' is a rigid type variable bound by the type signature for to ::
ClassB c => Test -> [c].
Referring to some similar questions on internet, I should remove the
(ClassB c) thing. Is this the only solution?
--
竹密岂妨流水过
山高哪阻野云飞
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
