[Haskell-cafe] Functor instance derived from Monad
frantisek at farka.eu
Wed Feb 19 22:25:30 UTC 2014
when reading the Functor-Applicative-Monad proposal  on Haskell
wiki I remembered that I have seen instance similar to
instance (Monad m) => Functor m where
fmap f a = a >>= \x -> return $ f x
with FlexibleInstances and UndecidableInstances language extensions.
But I cannot remember where it was nor can I find any useful reference.
Is there some library in Hackage with this and similar instances?
Can you point out some leading marks to me?
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