At Wed, 16 Apr 2014 09:02:44 -0400, Matthias Felleisen 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 :-)
I've pushed a repair for Asumu's example. The part of the optimizer that throws out unsafe operations with unused results could be triggered before the letrec-fixing pass, and the optimization wasn't as conservative as it needs to be at that point about local variables. _________________________ Racket Developers list: http://lists.racket-lang.org/dev
