[Haskell-cafe] What are the MonadPlus laws?

[ajb at spamcop.net]

G'day all.

Quoting Jules Bean <jules at jellybean.co.uk>:

> So, anyone? What are the laws that MonadPlus is supposed to satisfy?

The problem is this "law":

    m >>= \k -> mzero === mzero

I think this "law" is untrue for _all_ MonadPlus instances, and you can
trivially check this by setting m to bottom.

Cheers,
Andrew Bromage