[Haskell-cafe] What are the MonadPlus laws?

ajb at spamcop.net ajb at spamcop.net
Tue Jan 25 20:55:12 EST 2005

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.

Andrew Bromage

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