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

[Keean Schupke]

Daniel Fischer wrote:

> That's probably a misunderstanding due to the notation, in the [] 
> monad, it's
>
>just
>
>concat (map c (a ++ b)) = concat (map c a) ++ concat (Map c b),
>
>which is easily seen to be true (if applying c to an element of a causes an 
>error, neither side will go past that).
>
>Daniel
>  
>
So do we consider [] to be fail?, Monad.hs defines:

instance MonadPlus [] where
   mzero = []
   mplus = (++)

What would happen if this was the definition?

instance MonadPlus [] where
   mzero = []
   mplus a b
       | a == [] = b
       | otherwise = a

    Keean.