On 23 September 2011 21:25, Maciej Marcin Piechotka
The problem of backward compatibility have been the main obstacle against adopting Functor f => (Pointed f =>?) => Applicative f => Monad f.
This proposition is to add following default instances[1]:
Sorry, I'm confused! The [1] link is about default superclass instances, not default signatures. As I understand it, default superclass instances are not implemented yet. I fully support the general aim and default superclass instances look like a very sensible way of addressing the problem. It's just not clear to me how the default signatures you're suggesting here get us closer to the goal. Perhaps you can explain it a bit more. I suspect other people on this list don't quite get it either.
default fmap :: Applicative f => (a -> b) -> f a -> f b f `fmap` m = pure f <*> m default pure :: Monad f => a -> f a pure = return default (<*>) :: Monad f => f (a -> b) -> f a -> f b (<*>) = liftM2 ($)
Duncan