> On Sep 4, 2019, at 9:56 AM, John Cowan <xxxxxx@ccil.org> wrote:
>
> Walking the stack is inherently unportable, because trampolining or Cheney-on-the-MTA implementations don't have a stack as such; Chicken error tracebacks report the last N calls without regard to any notion of stack depth.

I’m talking about the conceptual Scheme stack (i.e. a frame for each non-tail call is added to the stack, and popped on return). This has a well-defined meaning at the Scheme level.  Obviously this is only portable to implementation of Scheme that have operators to introspect the continuation.  But SRFIs don’t necessarily have to be “100% portable”… they can go as far as suggest new features of Scheme to advance the language.

Marc