The difference is that every time that (list 1 2 3) is executed, you get a new different list. But with each '(1 2 3) you get every time the same list. The '(1 2 3) is referenced from the "source code" so it will not be collected. (A different copy of '(1 2 3) creates a different list, but always the same list.)
Gustavo ;--- #lang racket/base (define (get-list-123) (list 1 2 3)) (define (get-quote-123) '(1 2 3)) (define (get-quote-bis-123) '(1 2 3)) (eq? (get-list-123) (get-list-123)) ;==> #f (eq? (get-quote-123) (get-quote-123)) ;==> #t (eq? (get-list-123) (get-quote-123)) ;==> #f (equal? (get-list-123) (get-quote-123)) ;==> #t (eq? (get-quote-123) (get-quote-bis-123)) ;==> #f (equal? (get-quote-123) (get-quote-bis-123)) ;==> #t ;--- On Sat, Aug 2, 2014 at 3:05 PM, Evgeny Odegov <[email protected]> wrote: > Well, it turns out that objects like #(1 2 3) or '(1 2 3) > are not collected (optimizations?), but (vector 1 2 3) and > (list 1 2 3) are collected normally. It so happens that I tried #(1 2 3) > and '(1 2 3) first and came to the wrong conclusions :) > > > > >> > But in case of another kind of value >> >> What another kiind? Small numbers and some chars are not garbage >> collected. >> >> >> Sat, 02 Aug 2014 22:47:32 +0700 от Evgeny Odegov <[email protected]>: >>> >>> In the example, the value is box and triggering occurs almost >>> immediately after set!. >>> But in case of another kind of value, triggering doesn't occur or take >>> much longer. >>> Why? (Or maybe I do something wrong?) >>> >>>> Probably you want to do something like this, I guess. It creates a >>>> single thread that just waits until anything registered with >>>> an-executor is garbage and then runs the executors. They will run >>>> asynchronously, but perhaps that's okay for your usecase. >>>> >>>> Robby >>>> >>>> #lang racket >>>> (define an-executor (make-will-executor)) >>>> (void >>>> (thread >>>> (λ () >>>> (let loop () >>>> (will-execute an-executor) >>>> (loop))))) >>>> >>>> (define a-box (box #f)) >>>> (will-register an-executor >>>> a-box >>>> (λ (x) (printf "a-box is now garbage\n"))) >>>> (collect-garbage) (collect-garbage) (collect-garbage) >>>> (printf "breaking the link\n") >>>> (set! a-box #f) >>>> (collect-garbage) (collect-garbage) (collect-garbage) >>>> >>>> On Sat, Aug 2, 2014 at 7:31 AM, Roman Klochkov < [email protected] > >>>> wrote: >>>>> >>>>> So I can write >>>>> >>>>> (define (make-obj stream) >>>>> (define res (obj (open-output-file "out.dat"))) >>>>> (define will (make-will-executor)) >>>>> (will-register will res (lambda (x) (close-output-port (obj-file >>>>> x)))) >>>>> (thread (lambda () (let loop () (will-try-execute will) (sleep 1) >>>>> (loop))))) >>>>> >>>>> to make my objects? Additional threads don't hinder performance, do >>>>> they? >>>>> >>>>> Or should I somehow figure out if the thread is already running, don't >>>>> run >>>>> it and use common `will' for all objects? >>>>> >>>>> Sat, 2 Aug 2014 07:00:04 -0500 от Robby Findler >>>>> < [email protected] >: >>>>> >>>>> One way is to set up a separate thread to do that. >>>>> >>>>> The reason they are not called automatically is sometimes running the >>>>> procedure passed to will-register needs to access some shared state >>>>> and so your program must be allowed to be in control of the timing of >>>>> the executor. >>>>> >>>>> In this case, it sounds like you can run the executor at any time, so >>>>> just creating a thread to close the port inside my-obj should work >>>>> fine. >>>>> >>>>> Robby >>>>> >>>>> >>>>> On Sat, Aug 2, 2014 at 6:15 AM, Roman Klochkov < [email protected] > >>>>> wrote: >>>>>> >>>>>> Then how? >>>>>> >>>>>> Suppose I have >>>>>> (struct obj (file)) >>>>>> (define my-obj (obj (open-output-file "out.dat"))) >>>>>> >>>>>> What I have to write to close the file, when my-obj will be GC'ed? >>>>>> >>>>>> I can write >>>>>> (define will (make-will-executor)) >>>>>> (will-register will my-obj (lambda (x) (close-output-port (obj-file >>>>>> x)))) >>>>>> >>>>>> But as far as I understand, it will not be called until `will-execute' >>>>>> or >>>>>> `will-try-execute' will be manually called? >>>>>> >>>>>> Then how to call will-try-execute when GC is collecting my-obj? >>>>>> >>>>>> >>>>>> Sat, 2 Aug 2014 11:57:32 +0100 от Matthew Flatt < [email protected] >>>>>> >: >>>>>> >>>>>> No, use the safe "will executors" API, instead. >>>>>> >>>>>> The unsafe finalizer API is for low-level, atomic finalization. >>>>>> Closing a >>>>>> port can flush buffers and more, and it's not a good idea to do that >>>>>> in an >>>>>> unsafe atomic context. >>>>>> >>>>>>> On Aug 2, 2014, at 11:12 AM, Roman Klochkov < [email protected] > >>>>>>> wrote: >>>>>>> >>>>>>> I have a structure, that has a filestream inside it. File have to be >>>>>>> cosed, when the structure is not used anymore (so gargbage >>>>>>> collected). >>>>>>> >>>>>>> Is the best way to do >>>>>>> (require ffi/unsafe) >>>>>>> (register-finalizer my-obj >>>>>>> (lambda (x) (close-output-port (obj-file x)))) >>>>>>> >>>>>>> ? >>>>>>> >>>>>>> It seems doing right thing, but why `ffi/unsafe'? Is it OK, when my >>>>>>> program actually doesn't use FFI? >>>>>>> >>>>>>> >>>>>>> -- >>>>>>> Roman Klochkov >>>>>>> ____________________ >>>>>>> Racket Users list: >>>>>>> http://lists.racket-lang.org/users >>>>>> >>>>>> >>>>>> -- >>>>>> Roman Klochkov >>>>>> >>>>>> ____________________ >>>>>> Racket Users list: >>>>>> http://lists.racket-lang.org/users >>>>>> >>>>> >>>>> -- >>>>> Roman Klochkov >>>> >>>> ____________________ >>>> Racket Users list: >>>> http://lists.racket-lang.org/users >>> >>> ____________________ >>> Racket Users list: >>> http://lists.racket-lang.org/users >>> >> > > ____________________ > Racket Users list: > http://lists.racket-lang.org/users ____________________ Racket Users list: http://lists.racket-lang.org/users
