Tim, if you paste your code in the definitions in DrRacket (with the #lang racket line), and run it (as a module, thus), you obtain this in the interactions window: 3 10 6
The `3` is because of the `(add1 (call/cc ... 2)))` expression, which is reduced to `(add1 2)` with the side effect of recording the continuation in `ret`. The `10` corresponds to `(ret 9)`. On Tue, Dec 8, 2020 at 2:26 AM Tim Meehan <btmee...@gmail.com> wrote: > I've read a lot about call/cc, and each time wind up just moving on. So > this is an early New Year's resolution: getting a better understanding of > it. > > According to Wikipedia's page on continuations, the continuation of the > statement: > > ((call/cc f) e2) > > is: > > (lambda (c) (c e2)) > > #lang racket > (define ret #f) > (define ret2 (lambda (c) (add1 c))) > > (add1 > (call/cc > (lambda (k) > (set! ret k) ;; Now ret should be equivalent to ret2. > 2))) > > (ret 9) ;; Why does this print twice? > (ret2 5) ;; This only prints once, like I would have expected. > > -- > You received this message because you are subscribed to the Google Groups > "Racket Users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to racket-users+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/racket-users/CACgrOx%2BnXZpQv_MbDwdAZJSGpMiD%2BE1gB4YH8Rsb_y3%3D6RaAnQ%40mail.gmail.com > <https://groups.google.com/d/msgid/racket-users/CACgrOx%2BnXZpQv_MbDwdAZJSGpMiD%2BE1gB4YH8Rsb_y3%3D6RaAnQ%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/CABNTSaG1R9eM%3DSRjbmWcBKFMyzBTou7O%3D2_0jgDg2_2qSuLb%3Dg%40mail.gmail.com.
