[racket-users] Re: Racket v6.10

[Alex Harsanyi]

On Tuesday, August 1, 2017 at 4:59:14 AM UTC+8, Vincent St-Amour wrote:
> Racket version 6.10 is now available from
> 

I just updated to Racket 6.10 on Windows 10 and noticed a bug that causes a 
crash (access violation).  This happens when there is a symbolic link in a 
`make-directory*` call.  To reproduce it:

* OS is Windows 10 64 bit, Racket version is 6.10, 64 bit
* open a command window and 
* create a directory "mkdir c:/some_dir"
* create a link to that directory "mklink /d c:/some_dir_link c:/some_dir"
* In DrRacket, run the following:
(make-directory* "c:/some_dir_link/subdir")

The result is that DrRacket will crash.  Same happens with racket.exe and any 
application built with racket that uses `make-directory*` with a path that 
contains a link.

The make-directory* call works fine in Racket 6.9 on the same platform.

Best Regards,
Alex.

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Re: [racket-users] Racket v6.10

[Matthew Flatt]

At Mon, 31 Jul 2017 16:00:01 -0500, Vincent St-Amour wrote:
> * Internally, Racket's intermediate compatibility layer over
>   operating-system facilities has been moved into its own library,
>   "rktio" [...] we expect a new glitch or
>   two in less-common build and execution environments.

James Bornholt discovered and repaired a rktio-related bug that is
worse than the expected glitch:

  https://github.com/racket/racket/issues/1769

The bug affects programs that

 * are running on Linux;

 * use non-socket, OS-level streams that can block on input or output,
   such as pipes created by `subprocess` or `system` to communicate
   with another process;

 * attempt an input or output operation when the stream is not ready
   for reading or writing; and

 * close the stream before it is used in a ready state.

Under those circumstances, a stream that is created later can be
confused internally with the old one and be treated as not ready, even
if it is ready.

Sockets (including TCP connections) are not affected by the bug.
Programs running on a platform other than Linux are also unaffected.

We haven't yet decided on further action, such as a patched release. If
you think your program might be affected, the release managers would
appreciate a brief note letting us know --- either on-list or off-list
--- since that will help us gauge the bug's impact.

Thanks again to James for tracking down the problem!

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[racket-users] Racket Con Lightning Talks?

[Andrew Gwozdziewycz]

While I'm guessing the answer is "the schedule is too full" (and,
woah, does it look like an incredible lineup) does Racket Con have
room for lightning talks? Lightning talks, for those not familiar, are
typically casual, 5 minute presentations on a topic. If there is room,
and the stars align, it's possible that I'd have something small to
present. If not, I'm still looking forward to pretty much every one of
the speakers, so no worries at all.

Thanks,

Andrew

-- 
http://www.apgwoz.com

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Re: [racket-users] HtDP2e, exercise 9, image area

[Fernando Basso]

On Tuesday, August 15, 2017 at 12:01:25 PM UTC-3, Matthias Felleisen wrote:
> > On Aug 15, 2017, at 6:08 AM, Fernando Basso wrote:
> > 
> > Exercise 9: 
> > http://homedirs.ccs.neu.edu/matthias/HtDP2e/part_one.html#%28counter._%28exercise._arith-p1%29%29
> > 
> > Among other requirements, it says, “for an image, it uses the area”. Not 
> > sure whether I should _assume_ the image is a basic shape like a square or 
> > if something more advanced is expected.
> 
> 
> You may wish to re-read the section that introduces Images. I have changed 
> the prose of the exercise so that the various kinds of data link back to 
> their defining sections.



On Tuesday, August 15, 2017 at 12:01:25 PM UTC-3, Matthias Felleisen wrote:
> > On Aug 15, 2017, at 6:08 AM, Fernando Basso wrote:
> > 
> > Exercise 9: 
> > http://homedirs.ccs.neu.edu/matthias/HtDP2e/part_one.html#%28counter._%28exercise._arith-p1%29%29
> > 
> > Among other requirements, it says, “for an image, it uses the area”. Not 
> > sure whether I should _assume_ the image is a basic shape like a square or 
> > if something more advanced is expected.
> 
> 
> You may wish to re-read the section that introduces Images. I have changed 
> the prose of the exercise so that the various kinds of data link back to 
> their defining sections.

Ah, very good. So, “An Image is a visual, rectangular piece of data, for 
example, a photo or a geometric figure and its frame.”

Thanks a lot.

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[racket-users] '(sum-milt-iter three five a b sum1 sum2)'

['47squared' via Racket Users]

Hello gentleman,

Why isn't '(sum-milt-iter three five a b sum1 sum2)' evaluating to 23 given 
that  '(mult-sum 5)' and '(mult-sum 3)' return the right answer, namely 5 and 
18?

; linear iterative process for computing the sum of the multiples of 3 and 5 < 
10
#lang racket
(define (sum-mult three five)
  (sum-mult-iter three five 1 1 0 0))

(define (sum-mult-iter three five a b sum1 sum2)
  (cond
[(and (>= (* five b) 10)
  (> (* three a) 10)
  (+ sum1 sum2))]
[else
  (sum-mult-iter three five (+ a 1) (+ b 1) (+ sum1 (* three a)) (+ 
sum2 (* five b)))]))

; Ive spent some time trying to understand why '(+ sum1 sum2)' does not 
evaluate to 23, but I cannot see why.

given that:

(define (mult-sum five)
(mult-sum-iterator five 1 0) )
(define (mult-sum-iterator five b sum2)
   (if (>= (* five b) 10)
   sum2
  (mult-sum-iterator five (+ b 1) (+ sum2 (* five b

; test
> (milt-sum 5) ; 5

and likewise '(milt-sum three)' evaluates to 18.
(define (mult-sum three)
(mult-sum-iterator three 1 0) )
(define (mult-sum-iterator three a sum2)
   (if (>= (* five a) 10)
   sum2
  (mult-sum-iterator five (+ a 1) (+ sum2 (* five a
; test
> (mult-sum 3) ; 18

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Re: [racket-users] HtDP2e, exercise 9, image area

[Matthias Felleisen]

> On Aug 15, 2017, at 6:08 AM, Fernando Basso  
> wrote:
> 
> Exercise 9: 
> http://homedirs.ccs.neu.edu/matthias/HtDP2e/part_one.html#%28counter._%28exercise._arith-p1%29%29
> 
> Among other requirements, it says, “for an image, it uses the area”. Not sure 
> whether I should _assume_ the image is a basic shape like a square or if 
> something more advanced is expected.


You may wish to re-read the section that introduces Images. I have changed the 
prose of the exercise so that the various kinds of data link back to their 
defining sections. 

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Re: [racket-users] Menu bar won't show

[Matthew Flatt]

At Mon, 14 Aug 2017 20:11:14 -0400, James wrote:
> except that part of the 
> confusion here is that the left most menu still says "DrRacket" ( or "racket" 
> if run from the terminal) when this normally identifies the running program.  
> Is there a simple way to give my program a name which will display there?

When you run within DrRacket, the application menu will always say
"DrRacket". There's not a way to change that.

If you create an application (using "Create Executable..." in the
"Racket" menu), then when you run the application, the application menu
will show your application's name.

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[racket-users] HtDP2e, exercise 9, image area

[Fernando Basso]

Exercise 9: 
http://homedirs.ccs.neu.edu/matthias/HtDP2e/part_one.html#%28counter._%28exercise._arith-p1%29%29

Among other requirements, it says, “for an image, it uses the area”. Not sure 
whether I should _assume_ the image is a basic shape like a square or if 
something more advanced is expected.

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