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

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