>> (letrec ([x (if #t 8 x)]) x) ;==>8 It was a mistake. I thought that the “x: undefined; ...” error was an expansion-time error, not a run-time error.
(I expected an error, because the x in the else part is “undefined”, even if it’s never accessed.) Gustavo On Sat, Apr 19, 2014 at 1:02 PM, Robby Findler <ro...@eecs.northwestern.edu> wrote: > These seem correct to me. What were you expecting (and why?). > > Robby > > > On Saturday, April 19, 2014, Gustavo Massaccesi <gust...@oma.org.ar> wrote: >> >> I found another problem with the optimizer and the new undefined behavior. >> >> (letrec ([x (if #t 8 x)]) x) ;==>8 >> >> I also consider this correct in a strange sense :). >> >> Gustavo >> >> >> Welcome to Racket v6.0.1.4. >> > (letrec ([x x]) x) >> x: undefined; >> cannot use before initialization >> context...: >> C:\Program Files\Racket-6.0.1.4\collects\racket\private\misc.rkt:87:7 >> > (letrec ([x 5]) x) >> 5 >> > (letrec ([x (if #t 8 x)]) x) >> 8 >> > (letrec ([x (if #f 8 x)]) x) >> x: undefined; >> cannot use before initialization >> context...: >> C:\Program Files\Racket-6.0.1.4\collects\racket\private\misc.rkt:87:7 >> > >> >> >> On Wed, Apr 16, 2014 at 10:09 AM, Matthias Felleisen >> <matth...@ccs.neu.edu> wrote: >> > >> > Ah, too bad: >> > >> >> pkgs/racket-pkgs/racket-test/tests/racket/optimize.rktl >> >> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> >> --- OLD/pkgs/racket-pkgs/racket-test/tests/racket/optimize.rktl >> >> +++ NEW/pkgs/racket-pkgs/racket-test/tests/racket/optimize.rktl >> >> @@ -3416,5 +3416,16 @@ >> >> (read (open-input-bytes (get-output-bytes o)))))) >> >> >> >> ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; >> >> +;; Check that an unsufe opertion's argument is >> >> +;; not "optimized" away if it's a use of >> >> +;; a variable before definition: >> >> + >> >> +(err/rt-test (let () >> >> + (unsafe-fx+ x 1) >> >> + (define x 3) >> >> + x) >> >> + exn:fail:contract:variable?) >> >> + >> >> +;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; >> > >> > >> > :-) >> > >> > On Apr 16, 2014, at 9:02 AM, Matthias Felleisen <matth...@ccs.neu.edu> >> > wrote: >> > >> >> >> >> On Apr 15, 2014, at 9:29 PM, Asumu Takikawa <as...@ccs.neu.edu> wrote: >> >> >> >>> On 2014-04-15 18:13:31 -0400, claire alvis wrote: >> >>>> The push below includes changes to letrec expressions, internal >> >>>> definitions, units, classes, and certain ill-formed shared >> >>>> expressions so >> >>>> that they no longer leak the `undefined' value. >> >>> >> >>> This is great! (especially happy that TR, even with classes, doesn't >> >>> have to worry about #<undefined> anymore) >> >>> >> >>> BTW, I found this weird behavior: >> >>> >> >>> Welcome to Racket v6.0.1.3. >> >>> -> (require racket/unsafe/ops) >> >>> -> (let () (+ x 3) (define x 3) 5) >> >>> ; x: variable used before its definition [,bt for context] >> >>> -> (let () (unsafe-fx+ x 3) (define x 3) 5) >> >>> 5 >> >> >> >> >> >> I consider this correct in a strange sense. >> >> >> >> Interestingly enough, >> >> >> >>> (let () (displayln (unsafe-fx+ x 3)) (define x 3) 5) >> >> x: variable used before its definition >> >> context...: >> >> /Users/matthias/plt/racket/collects/racket/private/misc.rkt:87:7 >> >> >> >> which is good too. I don't know how Claire and Matthew did this, >> >> but it's good :-) >> >> _________________________ >> >> Racket Developers list: >> >> http://lists.racket-lang.org/dev >> > >> > _________________________ >> > Racket Developers list: >> > http://lists.racket-lang.org/dev >> _________________________ >> Racket Developers list: >> http://lists.racket-lang.org/dev _________________________ Racket Developers list: http://lists.racket-lang.org/dev
