[racket-users] folding xml - reprise
Hi, I'm trying to do something like a fold, but over a tree instead of a list. Is there anything like that? If it's unclear what I mean, there's a mechanism like that in guile: https://www.gnu.org/software/guile/manual/html_node/SXML-Tree-Fold.html They use it e.g. for XML transformations, but it's really a generic operation and quite useful. Here's a paper on it by Andy Wingo if anyone wants to know the theory behind: https://pdfs.semanticscholar.org/d41a/175cf5bf19c795b940edf566988df05ee4a1.pdf is there anything along those lines in Racket ? Thanks in advance -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/CAJ98PDyVHDnpusBQ9g%3D26J4W7GF5%2Be9krPvUCDuJHY94-17G6w%40mail.gmail.com.
Re: [racket-users] Gradual Typed Racket?
On Monday, March 23, 2020 at 9:59:22 PM UTC+1, Hendrik Boom wrote: > > On Mon, Mar 23, 2020 at 12:16:45PM -0400, Ben Greenman wrote: > > > > > Not sure about best practices, but I definitely prefer keeping typed > > and untyped code in separate modules. > > It can be veru useful to be able to mix them while in transition from one > to the other. > > -- hendrik > Absolutely! In my case I am writing code from scratch for my research (theoretical computer science), but I end up wanting to write some stuff which Typed Racket cannot type (converting to a polymorphic type variable, for example), or even stuff which is difficult to type without writing long dependent types. For these cases, I'd prefer to just drop the types "temporarily", which the different modules approach should probably allow me to do. - Sergiu -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/9bce12f3-fbba-4dec-b849-235ef573602c%40googlegroups.com.
[racket-users] Best way to say "terminate unless received by X time"
I've got this code: (thread (thunk (let loop () (define-values (len shost sport) (udp-receive! socket buffer)) ...do stuff with the received message... (loop I'd like to be able to say "If you haven't received a message in X time, kill the thread". I'm not sure how to enact that; sync/timeout won't do it since the thread won't return. I've thought of weird signaling systems using channels or set! on some external value or etc, but they are all terrible. What's the right way to do this? -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/CAE8gKocoTTN0VfOToioMq3xK_0ysqAQVHmZ%2BmiFS9iutzY0sxQ%40mail.gmail.com.
Re: [racket-users] Best way to say "terminate unless received by X time"
You can start a second thread that monitors the condition as well as a timer; if the timer goes off first, then you kill the first thread; if the condition happens first, then it continues. If you don't want the second thread to have to monitor the condition, then the first thread should tell the second thread that everything is okay, such as by setting a semaphore. Like this: ``` #lang racket/base (define (kill-unless-sema-after-secs t sema secs) (thread (λ () (sync sema (handle-evt (alarm-evt (+ (current-inexact-milliseconds) (* 1000 secs))) (λ _ (kill-thread t))) (module+ main (define t (thread (thunk (let loop () (define sema (make-semaphore)) (kill-unless-sema-after-secs t sema secs) (define-values (len shost sport) (udp-receive! socket buffer)) (semaphore-post sema) ;; xxx do stuff (loop)) ``` -- Jay McCarthy Associate Professor @ CS @ UMass Lowell http://jeapostrophe.github.io Vincit qui se vincit. On Tue, Mar 24, 2020 at 4:03 PM David Storrs wrote: > > I've got this code: > > (thread > (thunk > (let loop () > (define-values (len shost sport) (udp-receive! socket buffer)) > ...do stuff with the received message... > (loop > > I'd like to be able to say "If you haven't received a message in X time, kill > the thread". I'm not sure how to enact that; sync/timeout won't do it since > the thread won't return. I've thought of weird signaling systems using > channels or set! on some external value or etc, but they are all terrible. > > What's the right way to do this? > > -- > 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. > To view this discussion on the web visit > https://groups.google.com/d/msgid/racket-users/CAE8gKocoTTN0VfOToioMq3xK_0ysqAQVHmZ%2BmiFS9iutzY0sxQ%40mail.gmail.com. -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/CAJYbDam%3D7teWJun3zg3c4MBtV4Ew%2Bgv6-Zj9xE7LTBew92u9RQ%40mail.gmail.com.
Re: [racket-users] Best way to say "terminate unless received by X time"
On Tue, Mar 24, 2020 at 4:03 PM David Storrs wrote: > > I've got this code: > > (thread > (thunk > (let loop () > (define-values (len shost sport) (udp-receive! socket buffer)) > ...do stuff with the received message... > (loop > > I'd like to be able to say "If you haven't received a message in X time, kill > the thread". I'm not sure how to enact that; sync/timeout won't do it since > the thread won't return. I've thought of weird signaling systems using > channels or set! on some external value or etc, but they are all terrible. > > What's the right way to do this? > Not quite sure what you mean when you say "sync/timeout won't do it since the thread won't return." You'll know when you timed-out, so you can return in that case. Wouldn't something like this work? ``` (thread (λ () (let loop () (match (sync/timeout timeout (udp-receive!-evt socket buffer)) [(list len shost sport) ;; do stuff (loop)] [#f ;; timed out; exit the loop and the thread (void)] ``` Apologies if I've misunderstood you. - Jon -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/CAKfDxxzgwLVDH-YzNWnMkghy_bMXcMHsujhWAxqHH8U07drDYg%40mail.gmail.com.
Re: [racket-users] Best way to say "terminate unless received by X time"
Aha! I didn't know there was a udp-receive-evt. That's exactly what I needed, thank you. On Tue, Mar 24, 2020, 4:15 PM Jon Zeppieri wrote: > On Tue, Mar 24, 2020 at 4:03 PM David Storrs > wrote: > > > > I've got this code: > > > > (thread > > (thunk > > (let loop () > > (define-values (len shost sport) (udp-receive! socket buffer)) > > ...do stuff with the received message... > > (loop > > > > I'd like to be able to say "If you haven't received a message in X time, > kill the thread". I'm not sure how to enact that; sync/timeout won't do it > since the thread won't return. I've thought of weird signaling systems > using channels or set! on some external value or etc, but they are all > terrible. > > > > What's the right way to do this? > > > > Not quite sure what you mean when you say "sync/timeout won't do it > since the thread won't return." You'll know when you timed-out, so you > can return in that case. Wouldn't something like this work? > > ``` > (thread > (λ () >(let loop () > (match (sync/timeout timeout (udp-receive!-evt socket buffer)) >[(list len shost sport) > ;; do stuff > (loop)] >[#f > ;; timed out; exit the loop and the thread > (void)] > ``` > > Apologies if I've misunderstood you. > > - Jon > -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/CAE8gKoct6X870TF1Djh9xv6JHeV40Q%3Dzczi313Kt8RUFwGavYQ%40mail.gmail.com.
[racket-users] TR: Occurrence Typing with custom predicate
Hello, I'm trying to use occurrence typing for (Vectorof Symbol) or (Boxof Symbol). Creating a custom predicate for (Listof Symbol) seems to work: --- #lang typed/racket (: los? (-> Any Boolean : (Listof Symbol))) (define los? (lambda (seq) (and (list? seq) (andmap symbol? seq --- However I haven't been able to create one for vectors or boxes. None of the things I've tried will typecheck. Any pointers? -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/4dc451fd-da2c-4a3c-8bb6-222e6b3b972b%40googlegroups.com.
Re: [racket-users] TR: Occurrence Typing with custom predicate
On 3/24/20, mmcdan wrote: > Hello, > > I'm trying to use occurrence typing for (Vectorof Symbol) or (Boxof > Symbol). > > Creating a custom predicate for (Listof Symbol) seems to work: > --- > #lang typed/racket > > (: los? (-> Any Boolean : (Listof Symbol))) > (define los? > (lambda (seq) (and (list? seq) (andmap symbol? seq > --- > > However I haven't been able to create one for vectors or boxes. None of the > things I've tried will typecheck. Any pointers? Typed Racket can't be sure that untyped code won't change whats inside a mutable vector or box --- #lang racket (define v (vector 'A)) (define (set-v!) (vector-set! v 0 0)) (provide v set-v!) #lang typed/racket (require/typed "path-to-untyped.rkt" (v : (Vectorof Any)) (set-v! : (-> Void))) ;; suppose this worked (: vos (-> Any Boolean : (Vectorof Symbol))) (define (vos x) ) (cond [(vos? v) ;; v : (Vectorof Symbol) (set-v!) ;; v now contains an integer! ])) --- I don't know a work-around. I was hoping it could work for (Immutable-Vectorof Symbol), but I don't know what to use in place of `andmap`. -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/CAFUu9R6nYVHoKCFGbjD8Q%2Bs__z2Cep9rwvqRL6HyZCE5GnzyhA%40mail.gmail.com.
[racket-users] embedding Google Forms/YouTube/… in Scribble
Thank you for your very useful and timely addition to the great Scribble functionality. In this time of great need for on-line learning, it is much appreciated. I hope other additions (e.g. Numbas quiz embedding), will follow in the near future. Congratulations for all the great work, and good health for you all. Sincerely, E. Comer -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/0e83751e-1d91-46f8-9ecb-46a53611a77f%40googlegroups.com.
Re: [racket-users] TR: Occurrence Typing with custom predicate
Hello Ben, Good call. I didn't think about the mutability of the container's contents with respect to types. My goal is to create a type that represents an immutable container. After exploring, it looks like there is a workaround: In the case of Vector, I can create a struct to hold the vector-immutable. In the case of Box, the struct can itself can be considered the box. The struct automatically generates the occurrence type predicate. --- #lang typed/racket (struct VoS ([contents : (Immutable-Vectorof Symbol)])) (define test-vos (VoS (vector-immutable 'A))) (VoS? test-vos) ;; #t (VoS-contents test-vos) ;; '#(A) --- I'll start using structs more often, instead of the *of types directly. Thanks! On Tuesday, March 24, 2020 at 3:50:39 PM UTC-7, Ben Greenman wrote: > > On 3/24/20, mmcdan > wrote: > > Hello, > > > > I'm trying to use occurrence typing for (Vectorof Symbol) or (Boxof > > Symbol). > > > > Creating a custom predicate for (Listof Symbol) seems to work: > > --- > > #lang typed/racket > > > > (: los? (-> Any Boolean : (Listof Symbol))) > > (define los? > > (lambda (seq) (and (list? seq) (andmap symbol? seq > > --- > > > > However I haven't been able to create one for vectors or boxes. None of > the > > things I've tried will typecheck. Any pointers? > > Typed Racket can't be sure that untyped code won't change whats inside > a mutable vector or box > > --- > #lang racket > (define v (vector 'A)) > (define (set-v!) (vector-set! v 0 0)) > (provide v set-v!) > > #lang typed/racket > (require/typed "path-to-untyped.rkt" > (v : (Vectorof Any)) > (set-v! : (-> Void))) > > ;; suppose this worked > (: vos (-> Any Boolean : (Vectorof Symbol))) > (define (vos x) ) > > (cond > [(vos? v) > ;; v : (Vectorof Symbol) > (set-v!) > ;; v now contains an integer! > ])) > --- > > I don't know a work-around. > > I was hoping it could work for (Immutable-Vectorof Symbol), but I > don't know what to use in place of `andmap`. > -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/a9b1f475-24df-4d05-b979-001763edd0c1%40googlegroups.com.
