Re: Re[2]: [Haskell-cafe] Why do I have to specify (Monad m) here again?

David: Thanks again for your explanation

Because, in general, m isn't an instance of Monad.

Talking about my example: class (Monad m) => GetMV m a where ... instance GetMV m c where (2) (2) There are only 2 cases: ghc supposes m does instantiates Monad => success ghc doesn't suppose this => failure becuase the class head of GetMV does require it. fix: adding (Monad m) => (3) That's why it would be save to assume that the programmer doesn't want a failure but success. Thus ghc could infer (3) automatically but doesn't Do I still miss a point? Marc