Re: [Haskell-beginners] About monad

A 20/12/2012, às 14:07, Trung Quang Nguyen escreveu:

Hi all,

I saw this

• instance Monad Maybe where • return x = Just x • Nothing >>= f = Nothing • Just x >>= f = f x • fail _ = Nothing

I am wondering about the implementation of function (>>=). Why don't it be Just x >>= f = Just (f x)?

Any body knows about this?

That would be the implementation of fmap for Maybe: instance Functor Maybe where fmap _ Nothing = Nothing fmap f (Just a) = Just (f a) so, different behavior. best, Miguel