Am Mittwoch, 24. September 2008 11:36 schrieb Jason Dusek:

Whenever `fail` comes up, there are usually remarks to the effect that it doesn't really belong in the definition of `Monad`. Where does `fail` belong? Could it go in `Arrow`?

-- _jsn

In my opinion, fail s should be somehow equivalent to mzero for any string s. So it should go into MonadPlus. Or we should split MonadPlus into MonadZero (with mzero) and a reduced MonadPlus (with mplus) and then fail should obviously go into MonadZero. Best wishes, Wolfgang