[racket-users] Strange Loop talk about Racket is up
https://youtu.be/yU-HUb8Xykg I'd estimate 10-15min total overlaps with my RacketCon talk here and there, 25-30min is my take on metaprogramming, Lisps and, of course, Racket. Haven't watched it myself, yet - need some hard liquor to numb the pain of listening to ones own voice :) -- 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/7df34d8d-c18a-4164-8ce3-e7abfe86d63c%40googlegroups.com.
Re: [racket-users] Strange Loop registration
Thanks John! We've fixed the front page. RacketCon registration is now open at (linked from the RacketCon page): https://www.eventbrite.com/e/racketcon-2016-tickets-24349152972 We're very excited to announce that Emina Torlak will be giving the keynote this year, on Synthesis and Verification for All. We still have room in the schedule for more speakers. If you're interested, just let me know! See you in St. Louis! Vincent On Mon, 06 Jun 2016 14:53:51 -0500, 'John Clements' via Racket Users wrote: > > Strange Loop Registration is opening this Wednesday at Noon, and as I found > out to my chagrin last year, those tickets do sell out *extremely* quickly. > I see that the page for RacketCon is up, but I don’t think I’ve seen notice > of it on the users mailing list, and it also looks to me like the main page > (https://www.racket-lang.org/) implicitly suggests that it’s not happening, > since there’s no announcement in the “news” section and the list of prior > years doesn’t include 2015. > > Anyhow: if you’re planning to attend RacketCon 2016, and it’s going to be > co-located with Strange Loop, now’s the time to think about registering for > Strange Loop. > > Hope to see you there this year! > > John > > -- > 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. > For more options, visit https://groups.google.com/d/optout. -- 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. For more options, visit https://groups.google.com/d/optout.
[racket-users] Strange Loop registration
Strange Loop Registration is opening this Wednesday at Noon, and as I found out to my chagrin last year, those tickets do sell out *extremely* quickly. I see that the page for RacketCon is up, but I don’t think I’ve seen notice of it on the users mailing list, and it also looks to me like the main page (https://www.racket-lang.org/) implicitly suggests that it’s not happening, since there’s no announcement in the “news” section and the list of prior years doesn’t include 2015. Anyhow: if you’re planning to attend RacketCon 2016, and it’s going to be co-located with Strange Loop, now’s the time to think about registering for Strange Loop. Hope to see you there this year! John -- 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. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] Strange loop
Ah! Of course. I never would have thought of that. Thank you. -- 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. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] Strange loop
Brendan,
You are correct, your program did error when you applied `Lam-body` to a
non-`Lam`. What happened is that, in the process of printing the error
message, it tried to print that non-`Lam` value, which called your
custom printer, and so on.
Does that make sense?
Vincent
On Wed, 02 Mar 2016 16:08:04 -0600,
brendan wrote:
>
> Today I wrote and then fixed a bug that caused my program to enter an
> infinite loop for reasons I don't understand.
>
> The program is the output display formatting for a prototype relational
> lambda calculus interpreter. First I took my two structs, Lam and App (using
> symbols for variables), and implemented the gen:custom-write interface for
> both, essentially following the example in the documentation:
>
>
> #lang racket
>
> (define-struct Lam (var body)
> #:methods gen:custom-write [(define write-proc (λ (v port mode)
>(write-lam v port mode)))])
> (define-struct App (func arg)
> #:methods gen:custom-write [(define write-proc (λ (v port mode)
>(write-app v port mode)))])
>
> (define (write-lam v port mode)
> (define recur (make-recur port mode))
> (fprintf port "λ~a." (symbol->string (Lam-var v)))
> (recur (Lam-body v)))
>
> (define (write-app v port mode)
> (define recur (make-recur port mode))
> (write-string "(" port)
> (recur (App-func v))
> (write-string " " port)
> (recur (App-arg v))
> (write-string ")" port))
>
> (define (make-recur port mode)
> (define aux (case mode
> [(#t) (lambda (v) (write v port))]
> [(#f) (lambda (v) (display v port))]
> [else (lambda (v) (print v port mode))]))
> (λ (v)
> (if (symbol? v)
> (write-string (symbol->string v) port)
> (aux v
>
>
> It worked fine. Then I defined two new structs, Lam* and App*, representing
> how the written notation groups consecutive lambdas and consecutive
> applications together to save parentheses. I also wrote procedures to convert
> from the simple representation to the new one. Finally, I implemented
> gen:custom-write for the new structs:
>
>
> (define-struct Lam* (var* body) #:transparent
> #:methods gen:custom-write [(define write-proc (λ (v port mode)
>(write-lam* v port
> mode)))])
>
> (define-struct App* (body*) #:transparent
> #:methods gen:custom-write [(define write-proc (λ (v port mode)
>(write-app* v port
> mode)))])
>
> (define (write-lam* v port mode)
> (define recur (make-recur port mode))
> (define var-str (string-append* (map symbol->string (Lam*-var* v
> (fprintf port "λ~a." var-str)
> (recur (Lam*-body v)))
>
> (define (write-app* v port mode)
> (define recur (make-recur port mode))
> (define (space-recur v)
> (write-string " " port)
> (recur v))
> (define body* (App*-body* v))
>
> (write-string "(" port)
> (recur (car body*))
> (map space-recur (cdr body*))
> (write-string ")" port))
>
> (define (exp->exp* e)
> (match e
> [(Lam _ _)
> (define-values (var* body) (lam->var*+body e))
> (Lam* var* body)]
> [(App _ _)
> (App* (reverse (app->body* e)))]
> [else e]))
>
> (define (lam->var*+body e)
> (match e
> [(Lam v (and b (Lam _ _)))
> (define-values (var* body) (lam->var*+body b))
> (values (cons v var*) body)]
> [(Lam v b)
> (values (list v) (exp->exp* b))]))
>
> (define (app->body* e)
> (match e
> [(App (and e1 (App _ _)) e2)
> (cons (exp->exp* e2) (app->body* e1))]
> [(App e1 e2)
> (list (exp->exp* e2) (exp->exp* e1))]))
>
>
> Since I knew that the new method implementations would be pretty similar to
> the old ones, I followed my usual bad habit of cutting and pasting and then
> making changes. And as happens more than I like to admit, I missed something.
> Specifically, in the last line of write-lam*, where you now see Lam*-body, I
> left it as Lam-body. When I tried displaying some simple test data, it went
> into an infinite loop. When I tried to investigate with the debugger, I
> learned that you can't break out of a loop in the debugger.
>
> Anyway, long-story->short, I fixed the error, but now I'm puzzled. Shouldn't
> the program have stopped with an error message when Lam-body was applied to a
> non-Lam?
>
> --
> 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.
> For more options, visit https://groups.google.com/d/optout.
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[racket-users] Strange loop
Today I wrote and then fixed a bug that caused my program to enter an infinite
loop for reasons I don't understand.
The program is the output display formatting for a prototype relational lambda
calculus interpreter. First I took my two structs, Lam and App (using symbols
for variables), and implemented the gen:custom-write interface for both,
essentially following the example in the documentation:
#lang racket
(define-struct Lam (var body)
#:methods gen:custom-write [(define write-proc (λ (v port mode)
(write-lam v port mode)))])
(define-struct App (func arg)
#:methods gen:custom-write [(define write-proc (λ (v port mode)
(write-app v port mode)))])
(define (write-lam v port mode)
(define recur (make-recur port mode))
(fprintf port "λ~a." (symbol->string (Lam-var v)))
(recur (Lam-body v)))
(define (write-app v port mode)
(define recur (make-recur port mode))
(write-string "(" port)
(recur (App-func v))
(write-string " " port)
(recur (App-arg v))
(write-string ")" port))
(define (make-recur port mode)
(define aux (case mode
[(#t) (lambda (v) (write v port))]
[(#f) (lambda (v) (display v port))]
[else (lambda (v) (print v port mode))]))
(λ (v)
(if (symbol? v)
(write-string (symbol->string v) port)
(aux v
It worked fine. Then I defined two new structs, Lam* and App*, representing how
the written notation groups consecutive lambdas and consecutive applications
together to save parentheses. I also wrote procedures to convert from the
simple representation to the new one. Finally, I implemented gen:custom-write
for the new structs:
(define-struct Lam* (var* body) #:transparent
#:methods gen:custom-write [(define write-proc (λ (v port mode)
(write-lam* v port mode)))])
(define-struct App* (body*) #:transparent
#:methods gen:custom-write [(define write-proc (λ (v port mode)
(write-app* v port mode)))])
(define (write-lam* v port mode)
(define recur (make-recur port mode))
(define var-str (string-append* (map symbol->string (Lam*-var* v
(fprintf port "λ~a." var-str)
(recur (Lam*-body v)))
(define (write-app* v port mode)
(define recur (make-recur port mode))
(define (space-recur v)
(write-string " " port)
(recur v))
(define body* (App*-body* v))
(write-string "(" port)
(recur (car body*))
(map space-recur (cdr body*))
(write-string ")" port))
(define (exp->exp* e)
(match e
[(Lam _ _)
(define-values (var* body) (lam->var*+body e))
(Lam* var* body)]
[(App _ _)
(App* (reverse (app->body* e)))]
[else e]))
(define (lam->var*+body e)
(match e
[(Lam v (and b (Lam _ _)))
(define-values (var* body) (lam->var*+body b))
(values (cons v var*) body)]
[(Lam v b)
(values (list v) (exp->exp* b))]))
(define (app->body* e)
(match e
[(App (and e1 (App _ _)) e2)
(cons (exp->exp* e2) (app->body* e1))]
[(App e1 e2)
(list (exp->exp* e2) (exp->exp* e1))]))
Since I knew that the new method implementations would be pretty similar to the
old ones, I followed my usual bad habit of cutting and pasting and then making
changes. And as happens more than I like to admit, I missed something.
Specifically, in the last line of write-lam*, where you now see Lam*-body, I
left it as Lam-body. When I tried displaying some simple test data, it went
into an infinite loop. When I tried to investigate with the debugger, I learned
that you can't break out of a loop in the debugger.
Anyway, long-story->short, I fixed the error, but now I'm puzzled. Shouldn't
the program have stopped with an error message when Lam-body was applied to a
non-Lam?
--
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