Am Sa., 29. Okt. 2022 um 09:31 Uhr schrieb Shiro Kawai <xxxxxx@gmail.com>:
>
> Some random questions I can't figure out from the spec:
>
> - Is prompt-tag argument (call-with-continuation-prompt etc.) required to be an object created by make-continuation-prompt-tag, or can it be arbitrary object?

Yes; see "5.2 Entry format"

> - Is the type of objects created by make-continuation-prompt disjoint from other types?

> - Is the type of objects created by make-continuation-mark-key disjoint from other types?

This is not enforced because it is hard to give it any sense without a
closed-world assumption.

PS See here for a general attempt to address the problem:
https://srfi-email.schemers.org/srfi-224/msg/16842716/.