I used Racket v7.2, and here's the full transcription. I'm going to check
with the newest Racket.
shiro@scherzo:~/src/srfi-226$ racket
Welcome to Racket v7.2.
> (require racket/control)
> (define (print . xs) (for-each display xs) (newline))
> (define m (make-parameter 0))
> (define c #f)
> (define (foo)
(parameterize ((m 1))
(reset
(print 'a: (m))
(shift k (print 'b: (m)) (set! c k))
(print 'c: (m)))))
> (define (bar)
(parameterize ((m 2))
(c #f)))
> (foo)
a:1
b:1
> (bar)
c:2
On Fri, Nov 18, 2022 at 9:26 AM Marc Nieper-Wißkirchen <
marc.nie...@gmail.com> wrote:
> Thanks for the report, Shiro!
>
> I have to investigate Racket's behavior. In 11.3.2 of the Racket
> reference, it says: "If a continuation is captured during the
> evaluation of parameterize, invoking the continuation effectively
> re-introduces the parameterization, since a parameterization is
> associated to a continuation via a continuation mark (see Continuation
> Marks) using a private key." This seems to be consistent with SRFI
> 226 and its sample implementation, but not consistent with your Racket
> experiments.
>
> Am Fr., 18. Nov. 2022 um 20:07 Uhr schrieb Shiro Kawai <
> shiro.ka...@gmail.com>:
> >
> > It seems that there's a disagreement in how a delimited continuation
> captures dynamic environment, between Racket and srfi-226.
> >
> > Suppose the following code:
> >
> > ```
> > (define (print . xs) (for-each display xs) (newline))
> >
> > (define m (make-parameter 0))
> >
> > (define c #f)
> >
> > (define (foo)
> > (parameterize ((m 1))
> > (reset
> > (print 'a: (m))
> > (shift k (print 'b: (m)) (set! c k))
> > (print 'c: (m)))))
> >
> > (define (bar)
> > (parameterize ((m 2))
> > (c #f)))
> > ```
> >
> > With srfi-226 (using reset/shift as given in the srfi) reference
> implementation on Chez, I get this:
> >
> > ```
> > > (run foo)
> > a:1
> > b:1
> > > (run bar)
> > c:1
> > ```
> >
> > With Racket racket/control, I get this:
> >
> > ```
> > > (foo)
> > a:1
> > b:1
> > > (bar)
> > c:2
> > ```
> >
> > I'm switching Gauche's internals to srfi-226 based model, and I noticed
> the difference---the current released version of Gauche (relying on
> dynamic-wind to handle parameterization) works like Racket, while the
> srfi-226 based version (using dynamic env chain to keep parameters) works
> like srfi-226 reference implementation.
> >
> > I think srfi-226 behavior is more consistent (when the delimited
> continuation is invoked, it restores the dynamic environment of the
> continuation of reset), but is there a plausible explanation of Racket
> behavior?
> >
> > This difference actually caused a compatibility problem of an existing
> application so I want to understand it fully.
> >
> >
> >
> >
> >
> >
> >
>
