I could give an example, actually, which might make things clearer. Take one of my unfoldM's: unfoldM f base = do fb <- f base case fb of Nothing -> return [] Just (a, b) -> do rest <- unfoldM f b return (a : rest) Now, using the Identity monad I can write a wrapper for non-monadic f's: myUnfoldr f b = runIdentity (unfoldM (return . f) b) which works the same as a regular unfoldr. With a monadic function and a wrapper that uses the Identity monad, I can offer both monadic and non-monadic interfaces to the unfolding functionality that is only implemented once. Is this a good design idea? Are there better ones? Is myUnfoldr necessarily less efficient than a "normal" unfoldr that doesn't have monads underneath constraining evaluation order? -- Mark