I just pushed a commit that fixes this, as well as a test case based on your example. Sorry for the problem.
Jay On Tue, Oct 4, 2016 at 6:16 PM, Philip McGrath <phi...@philipmcgrath.com> wrote: > In #lang web-server, set! seems to behave differently with local vs. > top-level variables. For example: >> >> #lang web-server/base >> >> (define x 0) >> (displayln x) ;; displays 0 >> (set! x (add1 x)) >> (displayln x) ;; displays 1 >> (let () >> (define y 0) >> (displayln y) ;; displays 0 >> (set! y (add1 y)) >> (displayln y)) ;; still displays 0 > > > There is an obvious solution — don't use set! — but it was still not what I > was expecting. > > The documentation does say that "… the store is not serialized. If you rely > on the store you will be taking huge risks. You will be assuming that the > serialized continuation is invoked on the same server before the server is > restarted or the memory is garbage collected." But this doesn't seem to have > to do with serialization per se. The line "(set! y (add1 y))" expands to > this (thanks to the macro stepper): >> >> (let-values:130 ([(y) (#%app:178 (#%app:179 CLOSURE-ref:130 clsr:130 >> '0))]) >> (let-values:180 (((l111640:181) >> (lambda:182 (x111632) >> >> (with-continuation-mark lifted.0:31 '(#t (lambda (x111632))) (set! y >> x111632))))) >> (#%app:183 keyword-apply:130 >> l111640:181 kws:130 kw-vals:130 rst:130))) > > which as best as I can tell will have no effect, because it's "y" is local. > > Does anyone have a deeper standing of what's going on? > > If set! is supposed to work this way, I would propose at least adding a note > to the "usage considerations" for #lang web-server, and I might consider > more drastic action (e.g. having set! raise an syntax error if it's used in > a local context. > > Doing without set! is not a problem, but the fact that it does work as usual > at the top level (and REPL) makes it difficult to realize you have a bug, > e.g. when porting existing code. > > -- > -Philip > > -- > 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. > For more options, visit https://groups.google.com/d/optout. -- Jay McCarthy Associate Professor PLT @ CS @ UMass Lowell http://jeapostrophe.github.io "Wherefore, be not weary in well-doing, for ye are laying the foundation of a great work. And out of small things proceedeth that which is great." - D&C 64:33 -- 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. For more options, visit https://groups.google.com/d/optout.
