Am Mittwoch, 31. M�rz 2004 09:32 schrieben Sie: > On Wed, Mar 31, 2004 at 08:48:35AM +0200, Wolfgang Jeltsch wrote: > > > Now, as i think a little more about it, i believe what you want to do > > > makes no sense. The monad operation '>>=' works on monads over > > > *different* 'element' (i.e. argument) types (look at the type of > > > '>>='). Your implementation only works if argument types are the same. > > > I can't see how this can be generalized to different argument types > > > even if both are instances of class Ord. > > > > I disagree. AFAICS, his implementation also works with different element > > types. Am I overlooking something? > > I think the real issue is that you can't restrict the types on which > monad operates without modifying the Monad class.
Exactly. You would be able to define a meaningful Monad instance for Set if Monad would have an Ord restriction on its "element" types. But since Monad doesn't have this restriction, you cannot make a meaningful Monad instance of Set. > [...] Wolfgang _______________________________________________ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
