# Latest **URL:** https://racket.discourse.group/latest.md?page=12 [Latest](https://racket.discourse.group/latest.md) · [Categories](https://racket.discourse.group/categories.md) · [Tags](https://racket.discourse.group/tags.md) **Page:** 13 --- ## [Racket July Meet-up Boston Thursday, July 24 6:00pm](https://racket.discourse.group/t/racket-july-meet-up-boston-thursday-july-24-6-00pm/3863)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 0\ **Last updated:** [July 20, 2025, 5:26pm UTC](https://racket.discourse.group/t/racket-july-meet-up-boston-thursday-july-24-6-00pm/3863 "2025-07-20T17:26:51Z")
Racket July Meet-up Boston Thursday, July 24 6:00pm Northeastern University West Village H Room 366 Come one come all ! Racket fans, racket fledglings, the racket-curious among us. Come to talk about racket with peo… --- ## [Confused about setup for reader and expander for simple DSL](https://racket.discourse.group/t/confused-about-setup-for-reader-and-expander-for-simple-dsl/3859)
**Author:** [@ddrake](https://racket.discourse.group/u/ddrake)\ **Replies:** 14\ **Last updated:** [July 19, 2025, 11:11pm UTC](https://racket.discourse.group/t/confused-about-setup-for-reader-and-expander-for-simple-dsl/3859 "2025-07-19T23:11:13Z")
I'm working on the Beautiful Racket "wires" DSL without looking at his solution, or using the various br libraries -- I want to get things working using standard Racket and not rely on BR's syntactic sugar / setup. I ha… --- ## [Pattern matching k or more items](https://racket.discourse.group/t/pattern-matching-k-or-more-items/3860)
**Author:** [@jeh](https://racket.discourse.group/u/jeh)\ **Replies:** 3\ **Last updated:** [July 19, 2025, 7:58pm UTC](https://racket.discourse.group/t/pattern-matching-k-or-more-items/3860 "2025-07-19T19:58:03Z")
Given a pattern like (match '(1 2 3 4) \[(list 1 a ..3) a\] \[\_ 'else\]) in the above must the ..k form be a literal non-negative integer? Can k not be an identifier bound to a non-negative identifier? --- ## [Are temporary parameters a silly idea?](https://racket.discourse.group/t/are-temporary-parameters-a-silly-idea/3420)
**Author:** [@bakgatviooldoos](https://racket.discourse.group/u/bakgatviooldoos)\ **Replies:** 3\ **Last updated:** [July 18, 2025, 11:09pm UTC](https://racket.discourse.group/t/are-temporary-parameters-a-silly-idea/3420 "2025-07-18T23:09:06Z")
Hi, Racket Discourse. I am experimenting with ways of exposing mutable variables to programmers within the body of procedures which themselves build-up objects (by which I am implying, that it is difficult to percolate … --- ## [How to introduce new bindings without using \`define-\*\`?](https://racket.discourse.group/t/how-to-introduce-new-bindings-without-using-define/3856)
**Author:** [@bakgatviooldoos](https://racket.discourse.group/u/bakgatviooldoos)\ **Replies:** 2\ **Last updated:** [July 18, 2025, 5:13pm UTC](https://racket.discourse.group/t/how-to-introduce-new-bindings-without-using-define/3856 "2025-07-18T17:13:16Z")
Hi, Racket Discourse. I am curious about how one introduces a new binding into a definition context--if I am using these terms correctly. I am looking at defining out-parameters in Racket, but my method of introducing … --- ## [Whoa! Gift from students!](https://racket.discourse.group/t/whoa-gift-from-students/3778)
**Author:** [@jbclements](https://racket.discourse.group/u/jbclements)\ **Replies:** 4\ **Last updated:** [July 18, 2025, 9:40am UTC](https://racket.discourse.group/t/whoa-gift-from-students/3778 "2025-07-18T09:40:15Z")
Okay, this is hands-down the best gift I've ever gotten from students. --- ## [Out-parameters in Racket](https://racket.discourse.group/t/out-parameters-in-racket/3855)
**Author:** [@bakgatviooldoos](https://racket.discourse.group/u/bakgatviooldoos)\ **Replies:** 1\ **Last updated:** [July 16, 2025, 12:07pm UTC](https://racket.discourse.group/t/out-parameters-in-racket/3855 "2025-07-16T12:07:17Z")
Hi, Racket Discourse. Long time no see. I have C# coming out my ears, lately, so I thought to make a bit of a racket to clear the air... :drum:. I really enjoy using out-parameters in C#, and I think they make some nic… --- ## [Handin with racket instead of teaching languages:](https://racket.discourse.group/t/handin-with-racket-instead-of-teaching-languages/3854)
**Author:** [@jestarray](https://racket.discourse.group/u/jestarray)\ **Replies:** 1\ **Last updated:** [July 16, 2025, 10:29am UTC](https://racket.discourse.group/t/handin-with-racket-instead-of-teaching-languages/3854 "2025-07-16T10:29:08Z")
(check: :language 'racket :requires '() :eval? #t :output (string-append (symbol-\>string ASSIGNMENT-NAME) ".rkt") :create-text? #t :textualize? #f ;;raises exception for submissio… --- ## [Problem with actions in github](https://racket.discourse.group/t/problem-with-actions-in-github/3851)
**Author:** [@gus-massa](https://racket.discourse.group/u/gus-massa)\ **Replies:** 3\ **Last updated:** [July 15, 2025, 11:34pm UTC](https://racket.discourse.group/t/problem-with-actions-in-github/3851 "2025-07-15T23:34:26Z")
When I push a branch to my fork GitHub - gus-massa/racket: The Racket repository the actions/tests are not run. The test run when send a PR upstream. Do I have to enable them somewhere? PS: The tests run both in my for… --- ## [Racket v8.18 branching is done!](https://racket.discourse.group/t/racket-v8-18-branching-is-done/3853)
**Author:** [@jbclements](https://racket.discourse.group/u/jbclements)\ **Replies:** 0\ **Last updated:** [July 15, 2025, 11:26pm UTC](https://racket.discourse.group/t/racket-v8-18-branching-is-done/3853 "2025-07-15T23:26:51Z")
The release process for v8.18 has begun: release checkpoints have been created for all packages in the main distribution, and release branches have been created when necessary. You can go on using \`master\` branches as us… --- ## [Map versus for/list (& idiomatic Racket, the "for/..." zoo, etc)](https://racket.discourse.group/t/map-versus-for-list-idiomatic-racket-the-for-zoo-etc/3831)
**Author:** [@ddrake](https://racket.discourse.group/u/ddrake)\ **Replies:** 12\ **Last updated:** [July 15, 2025, 6:07pm UTC](https://racket.discourse.group/t/map-versus-for-list-idiomatic-racket-the-for-zoo-etc/3831 "2025-07-15T18:07:55Z")
I'm learning Racket, and I do know about functional programming, and have used and loved map (and its relatives) in many languages (Haskell, emacs lisp, Typescript/JS, Python, Julia...even C#, where they call it Select..… --- ## [\*\*Racket meet-up\*\*: Saturday, 5 July 2025 at 18:00 UTC](https://racket.discourse.group/t/racket-meet-up-saturday-5-july-2025-at-18-00-utc/3832)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 3\ **Last updated:** [July 13, 2025, 11:50am UTC](https://racket.discourse.group/t/racket-meet-up-saturday-5-july-2025-at-18-00-utc/3832 "2025-07-13T11:50:09Z")
Everyone is welcome to join us for the :racket: Racket meet-up: Saturday, 5 July 2025 at 18:00 UTC In your timezone: 2025-07-05T18:00:00Z (UTC). (converter). At this meet-up: in-person meet-ups being planned for SF a… --- ## [Scribble and plot/pict doesn't know about pi?](https://racket.discourse.group/t/scribble-and-plot-pict-doesnt-know-about-pi/3850)
**Author:** [@ddrake](https://racket.discourse.group/u/ddrake)\ **Replies:** 2\ **Last updated:** [July 12, 2025, 7:47pm UTC](https://racket.discourse.group/t/scribble-and-plot-pict-doesnt-know-about-pi/3850 "2025-07-12T19:47:16Z")
I'm experimenting with Scribble and wanted to see about including function plots. Something like this: #lang scribble/base @(require scribble/manual) @(require plot/pict) @title{Plots in Scribble} The sine function: … --- ## [Does anyone have a nix flake for racket and its lsp?](https://racket.discourse.group/t/does-anyone-have-a-nix-flake-for-racket-and-its-lsp/3849)
**Author:** [@nrs-status](https://racket.discourse.group/u/nrs-status)\ **Replies:** 1\ **Last updated:** [July 12, 2025, 4:04pm UTC](https://racket.discourse.group/t/does-anyone-have-a-nix-flake-for-racket-and-its-lsp/3849 "2025-07-12T16:04:38Z")
I'd like to run Racket on NixOS with neovim. I was wondering, does anyone have a working nix flake that will provide a shell with the lsp and the compiler? --- ## [Call for Papers: The 2025 Scheme and Functional Programming Workshop](https://racket.discourse.group/t/call-for-papers-the-2025-scheme-and-functional-programming-workshop/3847)
**Author:** [@youyoucong](https://racket.discourse.group/u/youyoucong)\ **Replies:** 0\ **Last updated:** [July 11, 2025, 11:00pm UTC](https://racket.discourse.group/t/call-for-papers-the-2025-scheme-and-functional-programming-workshop/3847 "2025-07-11T23:00:10Z")
CALL FOR PAPERS The 2025 Workshop on Scheme and Functional Programming Co-located with ICFP/SPLASH 2025 (Singapore) The 2025 Scheme and Functional Programming Workshop is calling for submissions. We invite high-qual… --- ## [Defining new special formatting escapes](https://racket.discourse.group/t/defining-new-special-formatting-escapes/3844)
**Author:** [@hendrikboom3](https://racket.discourse.group/u/hendrikboom3)\ **Replies:** 2\ **Last updated:** [July 11, 2025, 8:29pm UTC](https://racket.discourse.group/t/defining-new-special-formatting-escapes/3844 "2025-07-11T20:29:16Z")
Is it possible to define new special formatting escapes without rewriting fprintf and friends from scratch? I know it's possible to redefine how particular structures are printed, displayed, or written by adding a metho… --- ## [Get version from info.rkt](https://racket.discourse.group/t/get-version-from-info-rkt/3843)
**Author:** [@damien\_mattei](https://racket.discourse.group/u/damien_mattei)\ **Replies:** 6\ **Last updated:** [July 10, 2025, 10:13pm UTC](https://racket.discourse.group/t/get-version-from-info-rkt/3843 "2025-07-10T22:13:19Z")
hello, i have an info.rkt file in my package, that contains the version number, how can i retrieve it from my code?. #lang info .... (define version "10.3") ..... i can require the info.rkt file but the definition are… --- ## [Using \`check-equal?\` with minor variations in expected data?](https://racket.discourse.group/t/using-check-equal-with-minor-variations-in-expected-data/3840)
**Author:** [@greghendershott](https://racket.discourse.group/u/greghendershott)\ **Replies:** 8\ **Last updated:** [July 9, 2025, 4:21pm UTC](https://racket.discourse.group/t/using-check-equal-with-minor-variations-in-expected-data/3840 "2025-07-09T16:21:56Z")
I have a test, where the expected results are slightly different when run under an older version of something. I needed to adapt the test to deal with both older and newer expected values. So I (not proudly) changed the… --- ## [Lazily flattening trees with a gopher](https://racket.discourse.group/t/lazily-flattening-trees-with-a-gopher/3842)
**Author:** [@shawnw](https://racket.discourse.group/u/shawnw)\ **Replies:** 0\ **Last updated:** [July 8, 2025, 1:06pm UTC](https://racket.discourse.group/t/lazily-flattening-trees-with-a-gopher/3842 "2025-07-08T13:06:44Z")
One of the bits of Scheme code on Oleg Kiselyov's site is an implementation of flatten that uses delay to lazily do its thing: (define (flatten x) (define (does-flatten x) (if (not (pair? x)) x (cond … --- ## [DrRacket sometimes saves files in a binary format](https://racket.discourse.group/t/drracket-sometimes-saves-files-in-a-binary-format/3841)
**Author:** [@shawnw](https://racket.discourse.group/u/shawnw)\ **Replies:** 3\ **Last updated:** [July 8, 2025, 11:56am UTC](https://racket.discourse.group/t/drracket-sometimes-saves-files-in-a-binary-format/3841 "2025-07-08T11:56:44Z")
Once in a while when opening a Racket source file in emacs or other tools, it ends up being, not plain text, but something that registers as binary, though it appears mostly plain text. They start with: #reader(lib"read… --- ## [A function that recursively copies files and directories](https://racket.discourse.group/t/a-function-that-recursively-copies-files-and-directories/3829)
**Author:** [@indrjo](https://racket.discourse.group/u/indrjo)\ **Replies:** 3\ **Last updated:** [July 7, 2025, 6:20pm UTC](https://racket.discourse.group/t/a-function-that-recursively-copies-files-and-directories/3829 "2025-07-07T18:20:17Z")
I know there is the function copy-directory/files, but I want a function that while descending directories performs some tasks before copying (see actions-on-dir). Here is the code I have written so far. #lang racket (… --- ## [How to provide nested command usage message with \`command-line\`](https://racket.discourse.group/t/how-to-provide-nested-command-usage-message-with-command-line/3825)
**Author:** [@dannypsnl](https://racket.discourse.group/u/dannypsnl)\ **Replies:** 2\ **Last updated:** [July 7, 2025, 5:08pm UTC](https://racket.discourse.group/t/how-to-provide-nested-command-usage-message-with-command-line/3825 "2025-07-07T17:08:12Z")
In Racket, we can use command-line to create single command with some flags. I use (define args (command-line ...)) (match args \[(list "command1") ...\] \[(list "command2") ...\] \[(list "command3") ...\]) to create … --- ## [Performance difference - why?](https://racket.discourse.group/t/performance-difference-why/3839)
**Author:** [@hnmdijkema](https://racket.discourse.group/u/hnmdijkema)\ **Replies:** 4\ **Last updated:** [July 7, 2025, 2:30pm UTC](https://racket.discourse.group/t/performance-difference-why/3839 "2025-07-07T14:30:05Z")
I'm testing with an OO framework, and try to understand the performance difference between two implementations of a caller construct. I've narrowed the problem down to two simple tests: Test1 where I create some simple … --- ## [Is rackunit not supposed to work with typed Racket?](https://racket.discourse.group/t/is-rackunit-not-supposed-to-work-with-typed-racket/3836)
**Author:** [@hendrikboom3](https://racket.discourse.group/u/hendrikboom3)\ **Replies:** 2\ **Last updated:** [July 5, 2025, 1:48am UTC](https://racket.discourse.group/t/is-rackunit-not-supposed-to-work-with-typed-racket/3836 "2025-07-05T01:48:38Z")
I tried using rackunit with typed/racket: #lang typed/racket (require rackunit) (module+ test (check-true #t) ) I was granted the following obscure error message: ../../usr/local/racket/share/pkgs/rackunit-lib… --- ## [Returning defined syntax from a lambda expression](https://racket.discourse.group/t/returning-defined-syntax-from-a-lambda-expression/3835)
**Author:** [@hnmdijkema](https://racket.discourse.group/u/hnmdijkema)\ **Replies:** 2\ **Last updated:** [July 4, 2025, 10:40pm UTC](https://racket.discourse.group/t/returning-defined-syntax-from-a-lambda-expression/3835 "2025-07-04T22:40:54Z")
Suppose I want to return lexically scoped syntax from a defined function, e.g. like this: (define (a x) (define (b y) (\* y x)) (define h (make-hash)) (set! h 'b b) (define-syntax caller (syntax-rul… --- ## [Default non-keyword paraeters in type Racket](https://racket.discourse.group/t/default-non-keyword-paraeters-in-type-racket/3833)
**Author:** [@hendrikboom3](https://racket.discourse.group/u/hendrikboom3)\ **Replies:** 1\ **Last updated:** [July 4, 2025, 9:14am UTC](https://racket.discourse.group/t/default-non-keyword-paraeters-in-type-racket/3833 "2025-07-04T09:14:21Z")
How do you do an optional function parameter in Typed Racket? I want the paraneter NOT to be keyword parameter. I'm used to writing things like (define (foo a \[b d\]) ( ... and when i ask for the value of b, and I'v… --- ## [How to have macro use result of another macros expansion](https://racket.discourse.group/t/how-to-have-macro-use-result-of-another-macros-expansion/3830)
**Author:** [@sora22](https://racket.discourse.group/u/sora22)\ **Replies:** 0\ **Last updated:** [July 3, 2025, 5:10pm UTC](https://racket.discourse.group/t/how-to-have-macro-use-result-of-another-macros-expansion/3830 "2025-07-03T17:10:29Z")
I am currently trying to work with something I need to keep backwards compatible, and find myself wanting to write macros that depend on the output of another macros expansion. Is there any way to do that besides local-e… --- ## [Racket docker M1 Rosetta](https://racket.discourse.group/t/racket-docker-m1-rosetta/2947)
**Author:** [@jasonhemann](https://racket.discourse.group/u/jasonhemann)\ **Replies:** 7\ **Last updated:** [July 3, 2025, 11:00am UTC](https://racket.discourse.group/t/racket-docker-m1-rosetta/2947 "2025-07-03T11:00:36Z")
Thanks in advance. I'm having trouble w/racket specifically under docker emulating x86\_64. AFAIK everything else seems to be working fine. I saw @awiersdorf started a related discussion a while back. I'm seeing differ… --- ## [Racket v8.18 release has started](https://racket.discourse.group/t/racket-v8-18-release-has-started/3827)
**Author:** [@jbclements](https://racket.discourse.group/u/jbclements)\ **Replies:** 0\ **Last updated:** [July 2, 2025, 9:32am UTC](https://racket.discourse.group/t/racket-v8-18-release-has-started/3827 "2025-07-02T09:32:08Z")
The release process for v8.18 will begin in about \*two\* weeks (I'm out of the country for a bit). If you have any new features that you want in and are relatively close to to being done, now is a good time to do that.… --- ## [Proper usage of make-base-eval-factory](https://racket.discourse.group/t/proper-usage-of-make-base-eval-factory/3809)
**Author:** [@Laurent.O](https://racket.discourse.group/u/Laurent.O)\ **Replies:** 9\ **Last updated:** [July 2, 2025, 12:28am UTC](https://racket.discourse.group/t/proper-usage-of-make-base-eval-factory/3809 "2025-07-02T00:28:29Z")
Say I have a module my-pkg/foo.rkt which exports bar. The doc mypkg/scribblings/foo.scrbl uses scribble/example like: @(define (make-my-eval) (make-base-eval '(require "../foo.rkt"))) @examples\[#:eval (make-my-eval) b… [Previous page](https://racket.discourse.group/latest.md?page=11) [Next page](https://racket.discourse.group/latest.md?page=13)