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 <[email protected]> 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 [email protected]. > 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 [email protected]. 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.
