[Haskell-cafe] Re: what is inverse of mzero and return?

[Keean Schupke]

Just thinking about this, a monad is a Functor plus two 
natural-tranformations, Unit and Join. Is there an equivalent definition 
for MonadPlus... I am not sure I understand where MonadPlus comes from? 
Is it just a Functor and two different definitions of Unit and Join 
(from those chosen to be in the class Monad?)

    Keean.