[racket-users] Rackefest 2021 Amateur Night: Call for participation

[je...@lisp.sh]

Friday and Saturday, March 26 & 27, 2021 is the next edition of Racketfest, 
the little Racket conference that could. On the homepage (
https://racketfest.com) you'll see an impressive lineup of 22 (!) talks 
from a star-studded array of Racket enthusiasts of all kinds.

This year Racketfest goes online, to Gather, following the brilliant 
example of the 2020 RacketCon. It'll be in two 4-hour blocks:

+ Friday, March 26 from 20:00 to 23:59 Central European Time (14:00 to 
17:59 US Eastern Time; 06:00 to 10:00 Australian Eastern Time, Saturday, 
March 27)

+ Saturday, March 27, again from from 20:00 to 23:59 Central European Time

You need to register first (https://racketfest.com/register) before 
moseying into the Racketfest space in Gather Town. Please get a ticket by 
Thursday, March 25 AOE so that I can upload the final list of email 
addresses to Gather. If the price is a barrier, just let me know -- thanks 
to our generous sponsors, we are happy to offer some diversity tickets. 
Just write to organiz...@racketfest.com if you'd like to be considered for 
such a ticket.

AMATEUR NIGHT FOR RACKETEERS!!

The Racketfest Organizers
Offer a Fine Array of Racket
Amusements, Projects, Delights
in

GATHER.TOWN!!

A Chance to Show Your Skills,
Hidden Talents, and New Work in
the Racket Programming Language
& Mingle with Your Fellow Racketeers

-- The Racketfest Organizers

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Re: [racket-users] Possible bug when reading/writing large inexact numbers

[Sam Tobin-Hochstadt]

I believe it's 
https://github.com/racket/racket/commit/0561d71e60502fa857b0d169f64da723584d96d6

Sam

On Sun, Mar 7, 2021 at 8:52 PM Greg Rosenblatt  wrote:
>
> Great, thanks.  Out of curiosity, where in the reader was this bug 
> originally?  Can you point me to a diff?
>
> On Sunday, March 7, 2021 at 8:42:33 PM UTC-5 sorawe...@gmail.com wrote:
>>
>> This is already fixed. Racket 8.0 doesn't have this issue.
>>
>> On Mon, Mar 8, 2021 at 8:31 AM Greg Rosenblatt  wrote:
>>>
>>> Large inexact numbers may change values after a second round trip between 
>>> read and write.  I was expecting to reach a fixed point after the first 
>>> round trip.  Is this a bug?
>>>
>>> Welcome to Racket v7.8 [cs].
>>> > 4.57030e+53
>>> 4.5703e+53
>>> > 4.5703e+53
>>> 4.57029995e+53
>>>
>>> --
>>> You received this message because you are subscribed to the Google Groups 
>>> "Racket Users" group.
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>
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Re: [racket-users] Possible bug when reading/writing large inexact numbers

[Greg Rosenblatt]

Great, thanks.  Out of curiosity, where in the reader was this bug 
originally?  Can you point me to a diff?

On Sunday, March 7, 2021 at 8:42:33 PM UTC-5 sorawe...@gmail.com wrote:

> This is already fixed. Racket 8.0 doesn't have this issue.
>
> On Mon, Mar 8, 2021 at 8:31 AM Greg Rosenblatt  wrote:
>
>> Large inexact numbers may change values after a second round trip between 
>> read and write.  I was expecting to reach a fixed point after the first 
>> round trip.  Is this a bug?
>>
>> Welcome to Racket v7.8 [cs].
>> > 4.57030e+53
>> 4.5703e+53
>> > 4.5703e+53
>> 4.57029995e+53
>>
>> -- 
>> 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...@googlegroups.com.
>> To view this discussion on the web visit 
>> https://groups.google.com/d/msgid/racket-users/28f2c566-472f-48eb-881f-028dad5b1285n%40googlegroups.com
>>  
>> 
>> .
>>
>

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Re: [racket-users] Possible bug when reading/writing large inexact numbers

[Sorawee Porncharoenwase]

This is already fixed. Racket 8.0 doesn't have this issue.

On Mon, Mar 8, 2021 at 8:31 AM Greg Rosenblatt  wrote:

> Large inexact numbers may change values after a second round trip between
> read and write.  I was expecting to reach a fixed point after the first
> round trip.  Is this a bug?
>
> Welcome to Racket v7.8 [cs].
> > 4.57030e+53
> 4.5703e+53
> > 4.5703e+53
> 4.57029995e+53
>
> --
> 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
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> 
> .
>

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[racket-users] Possible bug when reading/writing large inexact numbers

[Greg Rosenblatt]

Large inexact numbers may change values after a second round trip between 
read and write.  I was expecting to reach a fixed point after the first 
round trip.  Is this a bug?

Welcome to Racket v7.8 [cs].
> 4.57030e+53
4.5703e+53
> 4.5703e+53
4.57029995e+53

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[racket-users] Do I need to explicitly enable readline support for the REPL?

[Tim Lee]

When I was using Racket v6, I had to add (require readline/rep) to my
~/.racketrc to enable readline support in the REPL. I have recently
upgraded to Racket v7.2 on Ubuntu 20.04. It seems that readline support
is automatically enabled even if I remove (require readline/rep) from
my ~/.racketrc.

Can anyone tell me what's going on? Did something in Racket change?

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Re: [racket-users] Racket slower than Chez Scheme on interpreter benchmark, potential low hanging fruit?

[Sorawee Porncharoenwase]

With the recent improvements by Phil, the rank of the syntax object variant
moves up from 26th to the second (what?!?), losing only to c++ / g++.
Moreover, it's significantly faster than the third place.

On Fri, Mar 5, 2021 at 3:29 AM philngu...@gmail.com <
philnguyen0...@gmail.com> wrote:

> Oh I see. So one problem is here that `match-define` expands to `match`
> with an implicit error case, which at the low level, isn't distinguished
> from a user-written second case, and the tag check can't just be eliminated.
>
> On Thursday, March 4, 2021 at 9:40:22 AM UTC-8 Sam Tobin-Hochstadt wrote:
>
>> I think there are two reasons that code gets slower.
>>
>> 1. The `match-define` includes pair and struct checks, which are
>> omitted for plain accessor uses because of the unsafe declaration.
>> 2. That use of `match` expands to `define-values` which ends up as a
>> `call-with-values` and a `case-lambda` at the chez layer and is not
>> removed.
>>
>> `match` could recognize that it's being compiled with unsafe mode and
>> omit these checks, although it's not that straightforward. Also
>> schemify (or Chez) could do more to eliminate the use of multiple
>> values, although that's hard without eliminating the failure cases.
>>
>> Sam
>>
>> On Thu, Mar 4, 2021 at 3:23 AM philngu...@gmail.com
>>  wrote:
>> >
>> > Thanks for the tip about PLT_CS_COMPILE_LIMIT! I submitted a revision
>> to the syntax object variant that incorporated sleepnova's and yjqww6's
>> improvements.
>> >
>> > Also, I never knew about `(#%declare #:unsafe)` until I saw yjqww6's
>> pull request. It makes a noticeable difference. One unsatisfying thing is
>> that in one place, if I replace the 4 separate define clauses with just
>> `(match-define (cons (op o val) rst) parsed)`, the benchmarks are more than
>> twice slower.
>> >
>> > On Wednesday, March 3, 2021 at 11:12:30 AM UTC-8 Sam Tobin-Hochstadt
>> wrote:
>> >>
>> >> First, there's no longer a difference because yjqww6 just had a PR
>> >> merged that improves the Racket performance.
>> >>
>> >> The performance difference that was there was mostly because the Chez
>> >> code was run with `--optimize-level 3` which turns off safety. If that
>> >> was changed to `--optimize-level 2` the timing became much slower.
>> >>
>> >> Sam
>> >>
>> >> On Mon, Mar 1, 2021 at 2:39 AM philngu...@gmail.com
>> >>  wrote:
>> >> >
>> >> > There’s this benchmark on BF interpreter where the Racket and Chez
>> Scheme implementations are very similar, but Chez Scheme is much faster
>> than Racket 8.0 at interpreting bench.b (3s vs 8s) and mandel.b (40s vs
>> 136s).
>> >> >
>> >> > There’s the “Racket (Syntax Object)” variant that directly parses
>> BF’s syntax into Racket syntax object, which is faster (3.7s for bench, 82s
>> for mandel), but still significantly behind Chez Scheme’s naive
>> interpreter.
>> >> >
>> >> > Profiling doesn’t give very illuminating results, saying most of the
>> cost is from interpreting BF’s loop instruction.
>> >> >
>> >> > Given that Racket is on Chez, could this benchmark reveal some low
>> hanging fruit for improving Racket’s performance?
>> >> >
>> >> > --
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[racket-users] Making sequences with missing values

[Raoul Schorer]

Hi,

I'd like missing values (NAs) *a la R* in sequences, such as a `bit-vector` 
with a 3rd NA value (therefore taking 2 bits/element and not 1). I'd like 
that for integers, flonums, etc. too. I'm trying to make a (struct seq/na 
(mask data)) with prop:sequence, separating the NA mask from the sequence 
elements and design `for` forms to iterate on those. Trying to follow the 
prop:sequence and for/fold/derived examples, I tried:

(struct bit-vector/na (missing bits)
  #:property prop:sequence
  (λ (i j) (in-parallel (bit-vector/na-missing i) (bit-vector/na-bits j

but that failed with:

../../../../usr/share/racket/collects/racket/private/for.rkt:488:5: 
sequence-property-guard: contract violation
  expected: (procedure-arity-includes/c 1)
  given: #

I understand the sequence interface is designed to consume a single element 
per iteration, but is there a way to achieve what I'd like?

Thanks!
Raoul

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