On Thu, Aug 19, 2010 at 6:26 AM, Ivan Lazar Miljenovic <ivan.miljenovic@gmail.com> wrote:

I'm trying to update container-classes to duplicate the pre-existing
classes defined in the Prelude (Functor, etc.) and am trying to get my
approach on how to have functions/classes that work on types of kind *
(e.g. Bytestring) as well as kind * -> * (e.g. lists), as my previous
approach didn't work.

This is exactly why the iteratee library provides a newtype wrapper around ByteString that adds a phantom type.

If I recall correctly, it looks like this (and probably adds some derived instances):

newtype WrappedByteString a = WBS ByteString

Haskell isn't friendly when it comes to kind polymorphism and I've never really seen a "solution" for it that I like.

And the above is actually something that may provide a nice addition to ByteString. You could track the encoding in the phantom type, potentially.

Jason