I want to declare the following:
class Get a where
ls :: a b -> IO [b]
mk :: IO [b] -> a b
instance (Get a) => Functor a where
fmap f x = mk (ls x >>= return . map f)
But to have ghc type everything, I have to turn on "-fglasgow-exts
-fallow-undecidable-instances -fallow-overlapping-instances".
Is there a clean way to state that all types in my type class are also
in the "Functor" type class?
If not, what is the problem?
Vincenzo
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