Re: [Haskell-cafe] Monadic tunnelling: the art of threading one monad through another

On Thu, 12 Jul 2007, Jules Bean wrote:

I think the best you can do is:

MonadIO io => (String -> io()) -> io ()

'MonadIO' lets you lift one way but not the other. Correct me if I'm wrong.

As for that: yes, that would be great. It would be great if more libraries made their callbacks had signatures like that.

Then these libraries would depend on MTL and thus on functional dependencies. It would be great if one could split MTL into a Haskell 98 part and a non-98 part.