> I haven't formally checked it, but I would bet that this endofunctor > over N, called Sign, is a monad:
Just to be picky a functor isn't a monad. A monad is a triple consisting of a functor and 2 natural transformations which make certain diagrams commute. If you are looking for examples, I always think that a partially ordered set is a good because the objects don't have any elements. A functor is then an order preserving map between 2 ordered sets and monad is then a closure (http://en.wikipedia.org/wiki/Closure_operator) - I didn't know this latter fact until I just looked it up. Dominic. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
