# Latest **URL:** https://racket.discourse.group/latest.md?page=39 [Latest](https://racket.discourse.group/latest.md) · [Categories](https://racket.discourse.group/categories.md) · [Tags](https://racket.discourse.group/tags.md) **Page:** 40 --- ## [Formatting negative numbers using \`~r\`](https://racket.discourse.group/t/formatting-negative-numbers-using-r/2354)
**Author:** [@alexh](https://racket.discourse.group/u/alexh)\ **Replies:** 1\ **Last updated:** [October 2, 2023, 9:30pm UTC](https://racket.discourse.group/t/formatting-negative-numbers-using-r/2354 "2023-10-02T21:30:05Z")
I was trying to format numbers using ~r to align them in a table, and noticed an unexpected, for me at least, result for negative numbers: the minus sign is put in front of the padding: \> (~r (- pi) #:precision 2 #:min-… --- ## [Getting (say) the month from a gregor datetime](https://racket.discourse.group/t/getting-say-the-month-from-a-gregor-datetime/2355)
**Author:** [@jbclements](https://racket.discourse.group/u/jbclements)\ **Replies:** 4\ **Last updated:** [October 2, 2023, 2:08pm UTC](https://racket.discourse.group/t/getting-say-the-month-from-a-gregor-datetime/2355 "2023-10-02T14:08:23Z")
I like the work and thought that went into gregor. However, I can't figure out how to extract (say) the month from a datetime without doing something crazy like comparing the date to the first of each month. Even that se… --- ## [Debugging input port](https://racket.discourse.group/t/debugging-input-port/2357)
**Author:** [@sorawee](https://racket.discourse.group/u/sorawee)\ **Replies:** 2\ **Last updated:** [October 2, 2023, 9:57am UTC](https://racket.discourse.group/t/debugging-input-port/2357 "2023-10-02T09:57:43Z")
Frequently, I get an error from (read in), but it's difficult to see what goes wrong. I can try to use peek-... on in to help debugging, but that's also not convenient because I need to specify how many bytes I want to r… --- ## [Parallel activity in the web-server for a game](https://racket.discourse.group/t/parallel-activity-in-the-web-server-for-a-game/2308)
**Author:** [@hendrikboom3](https://racket.discourse.group/u/hendrikboom3)\ **Replies:** 5\ **Last updated:** [October 2, 2023, 1:59am UTC](https://racket.discourse.group/t/parallel-activity-in-the-web-server-for-a-game/2308 "2023-10-02T01:59:03Z")
I'm still working on the minimal multiplayer game to be run from the Racket web-server. I have a few questions in the following big post, most of which is to establish context. I'm hung up on the various forms of paral… --- ## [\`ffi-lib\` fails to load an existing library](https://racket.discourse.group/t/ffi-lib-fails-to-load-an-existing-library/2353)
**Author:** [@Antigen-11](https://racket.discourse.group/u/Antigen-11)\ **Replies:** 7\ **Last updated:** [October 1, 2023, 4:19pm UTC](https://racket.discourse.group/t/ffi-lib-fails-to-load-an-existing-library/2353 "2023-10-01T16:19:40Z")
Hello, everyone! I create an application and use The Racket Foreign Interface to load foreign libraries. Here's part of the project after compiling c codes. ./gsl-fork/build/lib/ ├── libgsl.a ├── libgslcblas.a ├── lib… --- ## ["Filter" Match-Expander: Better Way to Achieve This?](https://racket.discourse.group/t/filter-match-expander-better-way-to-achieve-this/2352)
**Author:** [@bakgatviooldoos](https://racket.discourse.group/u/bakgatviooldoos)\ **Replies:** 4\ **Last updated:** [September 30, 2023, 6:25pm UTC](https://racket.discourse.group/t/filter-match-expander-better-way-to-achieve-this/2352 "2023-09-30T18:25:41Z")
Hi, Racket Discourse. I've been looking for a way to "filter" on certain patterns in lists in match-forms, somewhat like list-no-order, but more general in the sense that one can specify "indeterminate" arbitrarily dist… --- ## [How to make small executables?](https://racket.discourse.group/t/how-to-make-small-executables/2244)
**Author:** [@lewisl](https://racket.discourse.group/u/lewisl)\ **Replies:** 22\ **Last updated:** [September 28, 2023, 11:45pm UTC](https://racket.discourse.group/t/how-to-make-small-executables/2244 "2023-09-28T23:45:18Z")
The smallest executable I can get is about 49mb from nearly 60mb. it's clear that there is no pruning of unused packages, libraries, etc. I have used the two "old" tricks: use #lang racket/base and the demod trick for … --- ## [Can I use Racket to install packages for Chez Scheme for Racket?](https://racket.discourse.group/t/can-i-use-racket-to-install-packages-for-chez-scheme-for-racket/2345)
**Author:** [@lewisl](https://racket.discourse.group/u/lewisl)\ **Replies:** 5\ **Last updated:** [September 28, 2023, 6:50pm UTC](https://racket.discourse.group/t/can-i-use-racket-to-install-packages-for-chez-scheme-for-racket/2345 "2023-09-28T18:50:41Z")
I followed some instructions to build the Chez Scheme underneath Racket to get a Chez Scheme that runs natively on M1 processors and OSX. That worked and completed quickly, but it created a very non-standard build which… --- ## [Difference between for and for\*](https://racket.discourse.group/t/difference-between-for-and-for/2343)
**Author:** [@matteo-daddio](https://racket.discourse.group/u/matteo-daddio)\ **Replies:** 6\ **Last updated:** [September 27, 2023, 5:19pm UTC](https://racket.discourse.group/t/difference-between-for-and-for/2343 "2023-09-27T17:19:08Z")
Hello, I’m working with for expressions. In these examples in the racket guide sometimes it is used for and sometimes for\* and I can’t understand why. Matteo --- ## [Macro optimisation in Racket](https://racket.discourse.group/t/macro-optimisation-in-racket/2342)
**Author:** [@damien\_mattei](https://racket.discourse.group/u/damien_mattei)\ **Replies:** 2\ **Last updated:** [September 27, 2023, 9:24am UTC](https://racket.discourse.group/t/macro-optimisation-in-racket/2342 "2023-09-27T09:24:43Z")
hello, i need to optimise some scheme code i wrote. I can do that by "inlining macro expansion" and in other case by doing both and substituing procedure symbolic result instead of re-calculus all the numeric values at… --- ## [Rename-in with a generated identifier](https://racket.discourse.group/t/rename-in-with-a-generated-identifier/2340)
**Author:** [@damien\_mattei](https://racket.discourse.group/u/damien_mattei)\ **Replies:** 0\ **Last updated:** [September 26, 2023, 10:49am UTC](https://racket.discourse.group/t/rename-in-with-a-generated-identifier/2340 "2023-09-26T10:49:59Z")
\#lang racket (require "overload-by-recursive-functions.rkt") (overload-existing-procedure length vector-length (vector?)) ;(overload-existing-procedure length string-length (string?)) ; ;(length #(1 2 3 4)) ;(length '(1… --- ## [Using Hash-Tables as Multisets](https://racket.discourse.group/t/using-hash-tables-as-multisets/2333)
**Author:** [@bakgatviooldoos](https://racket.discourse.group/u/bakgatviooldoos)\ **Replies:** 1\ **Last updated:** [September 23, 2023, 9:15am UTC](https://racket.discourse.group/t/using-hash-tables-as-multisets/2333 "2023-09-23T09:15:32Z")
Hi, Racket Discourse. I have been thinking a lot about multisets recently, because I want to implement a particular "computer algebra" system which codifies arithmetic/algebra in terms of "closed-form numbers", to a deg… --- ## [Basic recursion: How to eliminate the \`reverse\` without relying on \`append\`?](https://racket.discourse.group/t/basic-recursion-how-to-eliminate-the-reverse-without-relying-on-append/2318)
**Author:** [@JohnSnow](https://racket.discourse.group/u/JohnSnow)\ **Replies:** 10\ **Last updated:** [September 23, 2023, 5:04pm UTC](https://racket.discourse.group/t/basic-recursion-how-to-eliminate-the-reverse-without-relying-on-append/2318 "2023-09-23T17:04:45Z")
I am processing some data and need to do a simple transformation, which can be simplified into a basic recursion problem. I have come up with a solution but I want to eliminate the 2 reverse, which are used to keep the … --- ## [Splicing in syntax](https://racket.discourse.group/t/splicing-in-syntax/2336)
**Author:** [@mem](https://racket.discourse.group/u/mem)\ **Replies:** 4\ **Last updated:** [September 23, 2023, 12:55pm UTC](https://racket.discourse.group/t/splicing-in-syntax/2336 "2023-09-23T12:55:19Z")
Be gentle, folks—first time posting here. I've been interested in DSLs for a long time, and when I get the itch I come back to Racket to fool around a bit and inevitably find myself tangled up in some issue or another. … --- ## [Racket Web Scraping](https://racket.discourse.group/t/racket-web-scraping/2326)
**Author:** [@bakgatviooldoos](https://racket.discourse.group/u/bakgatviooldoos)\ **Replies:** 6\ **Last updated:** [September 22, 2023, 6:09pm UTC](https://racket.discourse.group/t/racket-web-scraping/2326 "2023-09-22T18:09:25Z")
Hi, Racket Discourse. I would like to ask what the current state is of web scraping libraries in Racket, and whether it would be better to just roll my own. I am thinking about building some functionality to help my te… --- ## [Blogpost: Using metapict to draw hat tiling](https://racket.discourse.group/t/blogpost-using-metapict-to-draw-hat-tiling/2328)
**Author:** [@rdivyanshu](https://racket.discourse.group/u/rdivyanshu)\ **Replies:** 3\ **Last updated:** [September 22, 2023, 4:32am UTC](https://racket.discourse.group/t/blogpost-using-metapict-to-draw-hat-tiling/2328 "2023-09-22T04:32:07Z")
Hey everyone, I have written blog post about using metapict to draw hat tiling Drawing hat tiling using Racket --- ## [Plot library very slow with sqrt](https://racket.discourse.group/t/plot-library-very-slow-with-sqrt/2330)
**Author:** [@matteo-daddio](https://racket.discourse.group/u/matteo-daddio)\ **Replies:** 7\ **Last updated:** [September 21, 2023, 10:51pm UTC](https://racket.discourse.group/t/plot-library-very-slow-with-sqrt/2330 "2023-09-21T22:51:32Z")
Hello, I'm working with the Plot library and I have a problem. When I try to plot, for example, the square root, this function i really fast: (time (plot (function sqrt (- 0) 20))) \> cpu time: 359 real time: 358 … --- ## [Example: minimal multiplayer web framework](https://racket.discourse.group/t/example-minimal-multiplayer-web-framework/2306)
**Author:** [@hendrikboom3](https://racket.discourse.group/u/hendrikboom3)\ **Replies:** 2\ **Last updated:** [September 21, 2023, 8:47pm UTC](https://racket.discourse.group/t/example-minimal-multiplayer-web-framework/2306 "2023-09-21T20:47:54Z")
I'm building a small framework for a multiplayer game to be played among friends over the wide internet by having browsers connect to a specialized Racket web-server. It's going slowly. Most of the work is tracking dow… --- ## [Check-eq? not behaving properly in Typed Racket](https://racket.discourse.group/t/check-eq-not-behaving-properly-in-typed-racket/2327)
**Author:** [@shawnw](https://racket.discourse.group/u/shawnw)\ **Replies:** 3\ **Last updated:** [September 20, 2023, 6:52pm UTC](https://racket.discourse.group/t/check-eq-not-behaving-properly-in-typed-racket/2327 "2023-09-20T18:52:12Z")
Consider: #lang typed/racket/base (require typed/rackunit) (: hash-\>immutable-hash (All (k v) (-\> (HashTable k v) (Immutable-HashTable k v)))) (define (hash-\>immutable-hash htab) (if (immutable? htab) htab … --- ## [How do you specify student languages from VSCode/Vim/Emacs/etc?](https://racket.discourse.group/t/how-do-you-specify-student-languages-from-vscode-vim-emacs-etc/2324)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 8\ **Last updated:** [September 20, 2023, 4:01pm UTC](https://racket.discourse.group/t/how-do-you-specify-student-languages-from-vscode-vim-emacs-etc/2324 "2023-09-20T16:01:57Z")
Hi, How do you specify student languages from VSCode/Vim/Emacs/etc? Is #lang htdp/bsl correct for beginners student language? What #lang preamble specifies the other teaching languages you would normally specify via … --- ## [How to use \`splicing-syntax-parameterize\`?](https://racket.discourse.group/t/how-to-use-splicing-syntax-parameterize/2319)
**Author:** [@soegaard](https://racket.discourse.group/u/soegaard)\ **Replies:** 9\ **Last updated:** [September 18, 2023, 11:47am UTC](https://racket.discourse.group/t/how-to-use-splicing-syntax-parameterize/2319 "2023-09-18T11:47:16Z")
The form (syntax-parameterize (\[id expr\] ...) body-expr ...+) binds the ids during the expansion of the body expressions. I am looking for something that allows be to do the same, but can be used in an internal definiti… --- ## [OOPSLA23: Rhombus: A New Spin on Macros Without All the Parentheses](https://racket.discourse.group/t/oopsla23-rhombus-a-new-spin-on-macros-without-all-the-parentheses/2309)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 2\ **Last updated:** [September 17, 2023, 12:01pm UTC](https://racket.discourse.group/t/oopsla23-rhombus-a-new-spin-on-macros-without-all-the-parentheses/2309 "2023-09-17T12:01:26Z")
Rhombus: A New Spin on Macros Without All the Parentheses Rhombus is a new language that is built on Racket. It offers the same kind of language extensibility as Racket itself, but using traditional (infix) notation. Al… --- ## [Tutorial for using frog on Windows?](https://racket.discourse.group/t/tutorial-for-using-frog-on-windows/2310)
**Author:** [@bremner](https://racket.discourse.group/u/bremner)\ **Replies:** 3\ **Last updated:** [September 16, 2023, 12:58pm UTC](https://racket.discourse.group/t/tutorial-for-using-frog-on-windows/2310 "2023-09-16T12:58:15Z")
One of my students asked me if it was possible to use frog on Windows. I guess the answer is "yes, with sufficient effort", and I see some hints in the source about "python.exe", but I was curious if someone has a nic… --- ## [Comparison of code between Scheme+ (an enhanced scheme language) and Python](https://racket.discourse.group/t/comparison-of-code-between-scheme-an-enhanced-scheme-language-and-python/2317)
**Author:** [@damien\_mattei](https://racket.discourse.group/u/damien_mattei)\ **Replies:** 0\ **Last updated:** [September 16, 2023, 8:57am UTC](https://racket.discourse.group/t/comparison-of-code-between-scheme-an-enhanced-scheme-language-and-python/2317 "2023-09-16T08:57:10Z")
I present a comparison of the same algorithm between two languages: Python versus Scheme+, a language based and written in Scheme. The algorithm is based on fundamental deep learning : a multi-layer neural network simul… --- ## [Macro Expressiveness and Nesting](https://racket.discourse.group/t/macro-expressiveness-and-nesting/2313)
**Author:** [@bakgatviooldoos](https://racket.discourse.group/u/bakgatviooldoos)\ **Replies:** 0\ **Last updated:** [September 15, 2023, 3:27pm UTC](https://racket.discourse.group/t/macro-expressiveness-and-nesting/2313 "2023-09-15T15:27:17Z")
Hi, Racket Discourse. Might be I'm overthinking the situation, but I thought I would ask anyway. Is there a known theorem/result/conjecture about the expressiveness of macros, in terms of how many layers of nesting you… --- ## [RacketCon should have a live stream](https://racket.discourse.group/t/racketcon-should-have-a-live-stream/2307)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 1\ **Last updated:** [September 15, 2023, 4:19pm UTC](https://racket.discourse.group/t/racketcon-should-have-a-live-stream/2307 "2023-09-15T16:19:00Z")
I feel strongly about this. RacketCon should have a live stream. We are a global community and participation should not be restricted by geography. I know it’s expensive to arrange. I’m willing to put money where my mo… --- ## [Macro Monstrosity: Some Questions](https://racket.discourse.group/t/macro-monstrosity-some-questions/2311)
**Author:** [@bakgatviooldoos](https://racket.discourse.group/u/bakgatviooldoos)\ **Replies:** 5\ **Last updated:** [September 15, 2023, 2:45pm UTC](https://racket.discourse.group/t/macro-monstrosity-some-questions/2311 "2023-09-15T14:45:09Z")
Hi, Racket Discourse. I am busy writing an "interface" which allows me to use a macro-defined template to access the content of the equivalents of JSON objects, i.e., hasheq tables, returned by http-easy's response-json … --- ## [What is the Racket roadmap?](https://racket.discourse.group/t/what-is-the-racket-roadmap/2204)
**Author:** [@joeld](https://racket.discourse.group/u/joeld)\ **Replies:** 28\ **Last updated:** [September 11, 2023, 9:31pm UTC](https://racket.discourse.group/t/what-is-the-racket-roadmap/2204 "2023-09-11T21:31:32Z")
I’ve been saving this question for the RacketCon town hall, but the more I think about it, it’s probably worth asking ahead of time. Hopefully I can ask it in a way that generates productive discussion. What improvement… --- ## [Updating announcement and information -type posts](https://racket.discourse.group/t/updating-announcement-and-information-type-posts/2305)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 2\ **Last updated:** [September 12, 2023, 2:03pm UTC](https://racket.discourse.group/t/updating-announcement-and-information-type-posts/2305 "2023-09-12T14:03:52Z")
Hi, 'Discourse tip'! While it is appropriate to email changes for mailing list users, I'd encourage posters to also edit the original announcements to fix text or broken links to make it easier for those who find your … --- ## [\[ANN\] A pretty expressive printer](https://racket.discourse.group/t/ann-a-pretty-expressive-printer/2094)
**Author:** [@sorawee](https://racket.discourse.group/u/sorawee)\ **Replies:** 3\ **Last updated:** [September 11, 2023, 11:03pm UTC](https://racket.discourse.group/t/ann-a-pretty-expressive-printer/2094 "2023-09-11T23:03:05Z")
Announcing pretty-expressive, a pretty printer based on our paper, A pretty expressive printer\[1\], which is to appear in the upcoming OOPSLA'23. The precursor of this pretty printer, pprint-compact, will be deprecated, … [Previous page](https://racket.discourse.group/latest.md?page=38) [Next page](https://racket.discourse.group/latest.md?page=40)