[Haskell-cafe] What are the MonadPlus laws?

Jules Bean jules at jellybean.co.uk
Tue Jan 25 13:21:47 EST 2005

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

The obvious ones are that if MonadPlus m then for all types a, (m a) 
should be a monoid. But, what about the others, because IO does not 
appear to satisfy

a >> mzero == mzero


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