On Mon, Jan 9, 2017 at 1:32 PM, Richard Eisenberg
2. Defaulting to the implementation written in the class (or `error "undefined method"` in the absence of a default. This is essentially the default default.)
I want to be able to specify that a certain default definition is good enough not to worry about. For example (with horribly bad syntax), class Applicative m => Monad m where (>>=) :: m a -> (a -> m b) -> m b m >>= f = join (f <$> m) -- plain old default join :: m (m a) -> m a good_enough_default join = (>>= id) This would allow users to just write newtype Foo a = Foo ... deriving Monad which would then be equivalent (using the notation you came up with) to instance Monad Foo where deriving newtype (>>=) David Feuer