[Haskell] Re: MonadPlus

Ashley Yakeley ashley at semantic.org
Sat Apr 30 17:33:44 EDT 2005

In article <4f386ed173562cddfbf16258f3b57a37 at alum.mit.edu>,
 Jan-Willem Maessen <jmaessen at alum.mit.edu> wrote:

> And the binary operation in a Magma has *no* properties.  My feeling is 
> that there MonadPlus must have *some* set of properties in order to be 
> useful---otherwise it's just an ad-hoc mechanism to call a pile of 
> different binary operations "mplus".  I think most people would agree 
> that's undesiriable, and the only confusion is which properties must 
> hold.
> I claim "monoid" is a point of agreement, at least.

I think Left Zero is too. I'd be very interested in what people feel 
constitutes a real MonadPlus: my own preference is Monoid, Left Zero, 
and Left Distribution.

Ashley Yakeley, Seattle WA

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