On Fri, 23 Jan 2009, Derek Elkins wrote:
mempty `mappend` undefined = undefined (left identity monoid law) The above definition doesn't meet this, similarly for the right identity monoid law. That only leaves one definition, () `mappend` () = () which does indeed satisfy the monoid laws.
So the answer to the question is "Yes." Another example of making things as lazy as possible going astray.
I'd like to argue that laws, such as monoid laws, do not apply to partial values. But I haven't thought my position through yet. -- Russell O'Connor http://r6.ca/ ``All talk about `theft,''' the general counsel of the American Graphophone Company wrote, ``is the merest claptrap, for there exists no property in ideas musical, literary or artistic, except as defined by statute.''