Lambda the Ultimate

Take the case of using continuations to implement coroutines: when a coroutine yields, do we really want to run unwind handlers (i.e. dynamic-wind)? After all, we are still "in" the coroutine, only its execution has been suspended, and is expected to continue at the point of suspension. It would seem strange to run the unwind handlers in this case, no?

Would it make sense to have two forms:

• (dynamic-wind pre-thunk thunk post-thunk) as in Scheme: pre and post thunks are always performed, whether control enters/exits the thunk normally, or through an exception, or through continuation capture.
• (unwind-protect thunk post-thunk) as in Common Lisp: post thunk is not performed if control exits thunk through continuation capture, only if it exits normally or through an exception.