Peter,

> Now, some implementations *do* add operations that are done
> specifically on continuations. The two types I know about are
>
> * Marc Feeley's continuation API, seen in (chicken continuation) [1]
>   and in Gambit. These are not procedure objects, so (continuation?
>   (call/cc (lambda (x) x))) returns false.
> * SRFI 226 [2]. In that SRFI, continuations are procedures.
>
> This is to support operations such as
> continuation-graft/call-in-continuation.

Add TinyScheme to that list, though it’s not a proper R7RS
implementation (yet.) It has a distinct continuation type, at the very
least.

But I did re-read the spec
https://standards.scheme.org/r7rs-html5/index.html#call-with-current-continuation
and the language is pretty clear:

> The procedure call-with-current-continuation (or its equivalent
> abbreviation call/cc) packages the current continuation (see the
> rationale below) as an “escape procedure” and passes it as an argument
> to proc. The escape procedure is a Scheme procedure that, if it is
> later called, will abandon whatever continuation is in effect at that
> later time and will instead use the continuation that was in effect
> when the escape procedure was created.

It is indeed just a procedure that call/cc passes into its argument, and
not the continuation itself.

Alright, continuation? is safe to remove too. Will not be there in the
next draft!

Best of luck,
--
Artyom Bologov
https://aartaka.me