[racket-dev] weak boxes in a script
I'm seeing a difference between when the value in a weak box is collected. When I run the following interactively, the value is collected like I expect. But it is not collected when running in a script, or in DrRacket. This is v5.1 on Ubuntu x64, compiled from source. Can someone explain the difference? ~$ racket Welcome to Racket v5.1. (define b (make-weak-box 'not-used)) (weak-box-value b) 'not-used (collect-garbage) (weak-box-value b) #f ~$ cat weak-box.rkt #lang racket (define b (make-weak-box 'not-used)) (weak-box-value b) (collect-garbage) (weak-box-value b) ~$ racket weak-box.rkt 'not-used 'not-used Thanks, Dave _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/dev
Re: [racket-dev] weak boxes in a script
David, I believe you are seeing the difference between modules and the REPL. At the REPL, each expression is compiled, run, and discarded. This yields the behavior you expect. But a #lang form produces a module, which is compiled and kept for the rest of the session. Thus, even after garbage collection, the compiled form of the first term still exists: (define b (make-weak-box 'not-used)) Thus there is a reference to the symbol not-used, and it is not garbage collected. Carl Eastlund On Wed, Mar 16, 2011 at 5:09 PM, David Vanderson david.vander...@gmail.com wrote: I'm seeing a difference between when the value in a weak box is collected. When I run the following interactively, the value is collected like I expect. But it is not collected when running in a script, or in DrRacket. This is v5.1 on Ubuntu x64, compiled from source. Can someone explain the difference? ~$ racket Welcome to Racket v5.1. (define b (make-weak-box 'not-used)) (weak-box-value b) 'not-used (collect-garbage) (weak-box-value b) #f ~$ cat weak-box.rkt #lang racket (define b (make-weak-box 'not-used)) (weak-box-value b) (collect-garbage) (weak-box-value b) ~$ racket weak-box.rkt 'not-used 'not-used Thanks, Dave _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/dev
Re: [racket-dev] weak boxes in a script
Thanks so much, that makes perfect sense. On 03/16/2011 02:16 PM, Carl Eastlund wrote: David, I believe you are seeing the difference between modules and the REPL. At the REPL, each expression is compiled, run, and discarded. This yields the behavior you expect. But a #lang form produces a module, which is compiled and kept for the rest of the session. Thus, even after garbage collection, the compiled form of the first term still exists: (define b (make-weak-box 'not-used)) Thus there is a reference to the symbol not-used, and it is not garbage collected. Carl Eastlund On Wed, Mar 16, 2011 at 5:09 PM, David Vanderson david.vander...@gmail.com wrote: I'm seeing a difference between when the value in a weak box is collected. When I run the following interactively, the value is collected like I expect. But it is not collected when running in a script, or in DrRacket. This is v5.1 on Ubuntu x64, compiled from source. Can someone explain the difference? ~$ racket Welcome to Racket v5.1. (define b (make-weak-box 'not-used)) (weak-box-value b) 'not-used (collect-garbage) (weak-box-value b) #f ~$ cat weak-box.rkt #lang racket (define b (make-weak-box 'not-used)) (weak-box-value b) (collect-garbage) (weak-box-value b) ~$ racket weak-box.rkt 'not-used 'not-used Thanks, Dave _ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/dev
