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

In article <200501231755.45127.jadrian@mat.uc.pt>, Jorge Adriano Aires wrote:

I just checked the paper, "A monadic Interpretation of Tatics", by Andrew Martin and Jeremy Gibbons http://web.comlab.ox.ac.uk/oucl/work/jeremy.gibbons/publications/tactics.pdf

And in deed, these are the listed laws for MonadPlus. On the other hand, Maybe is said to be an instance of MonadPlus.

So now I'm lost.

OK, Martin and Gibbons are to blame, then. I like their list or laws, but they're wrong to say that Maybe satisfies those laws. -- Ashley Yakeley, Seattle WA