# Latest **URL:** https://racket.discourse.group/latest.md?page=14 [Latest](https://racket.discourse.group/latest.md) · [Categories](https://racket.discourse.group/categories.md) · [Tags](https://racket.discourse.group/tags.md) **Page:** 15 --- ## [Why is contract-out struct immutable?](https://racket.discourse.group/t/why-is-contract-out-struct-immutable/3755)
**Author:** [@mike](https://racket.discourse.group/u/mike)\ **Replies:** 2\ **Last updated:** [May 22, 2025, 6:18am UTC](https://racket.discourse.group/t/why-is-contract-out-struct-immutable/3755 "2025-05-22T06:18:29Z")
It seems struct in contract-out does not support the #:mutable option. Why is that? This is especially strange as struct/contract does support it. This is regrettable, as changing one into the other is super-tedious. I… --- ## [USB and console-mode support](https://racket.discourse.group/t/usb-and-console-mode-support/3700)
**Author:** [@HughAguilar](https://racket.discourse.group/u/HughAguilar)\ **Replies:** 26\ **Last updated:** [May 22, 2025, 5:15am UTC](https://racket.discourse.group/t/usb-and-console-mode-support/3700 "2025-05-22T05:15:39Z")
I need to write a terminal program. I already have a program written in Python (not by me) but it would need significant upgrading and I don't want to learn enough Python to do this (Python is really not my kind of langu… --- ## [Scramble/regexp question](https://racket.discourse.group/t/scramble-regexp-question/3319)
**Author:** [@jbclements](https://racket.discourse.group/u/jbclements)\ **Replies:** 9\ **Last updated:** [May 21, 2025, 4:28pm UTC](https://racket.discourse.group/t/scramble-regexp-question/3319 "2025-05-21T16:28:04Z")
I've just started using Ryan Culpepper's scramble/regexp library for constructing regular expressions in a structured way (a la "SRE"s), and I'm liking it a lot. One thing I haven't figured out yet is a nice way to write… --- ## [Racket upgrade (8.17) with Emacs racket-mode - the curse of racket-mode-start-faster](https://racket.discourse.group/t/racket-upgrade-8-17-with-emacs-racket-mode-the-curse-of-racket-mode-start-faster/3750)
**Author:** [@maueroats](https://racket.discourse.group/u/maueroats)\ **Replies:** 1\ **Last updated:** [May 19, 2025, 8:42pm UTC](https://racket.discourse.group/t/racket-upgrade-8-17-with-emacs-racket-mode-the-curse-of-racket-mode-start-faster/3750 "2025-05-19T20:42:20Z")
Install Racket 8.17 and now emacs won't start my Racket REPL. I did migrate everything from my previous version and did not touch the emacs config. Suggestions? --- ## [Structure constructor](https://racket.discourse.group/t/structure-constructor/3748)
**Author:** [@hendrikboom3](https://racket.discourse.group/u/hendrikboom3)\ **Replies:** 1\ **Last updated:** [May 19, 2025, 12:27am UTC](https://racket.discourse.group/t/structure-constructor/3748 "2025-05-19T00:27:02Z")
Let's define a structure type (struct onion (leek cut tears)) Now I'd like to construct a value of this type. I can say (onion 1 2 4) but if there are a lot of components it can become obscure which value goes with… --- ## [Racket v8.17 is now available](https://racket.discourse.group/t/racket-v8-17-is-now-available/3747)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 1\ **Last updated:** [May 17, 2025, 7:06pm UTC](https://racket.discourse.group/t/racket-v8-17-is-now-available/3747 "2025-05-17T19:06:02Z")
We are pleased to announce Racket v8.17 is now available from https://download.racket-lang.org/. As of this release: The new drracket-core package provides a version of drracket with a smaller set of dependencies. Typ… --- ## [What're Differences Between \`typed/racket/unsafe\` and \`typed/racket/optional\`?](https://racket.discourse.group/t/whatre-differences-between-typed-racket-unsafe-and-typed-racket-optional/3746)
**Author:** [@NoahStoryM](https://racket.discourse.group/u/NoahStoryM)\ **Replies:** 1\ **Last updated:** [May 16, 2025, 12:50pm UTC](https://racket.discourse.group/t/whatre-differences-between-typed-racket-unsafe-and-typed-racket-optional/3746 "2025-05-16T12:50:39Z")
I'm writing a module that adds types to identifiers imported from untyped code, and I want to avoid contract generation. I see two approaches: Using typed/racket/unsafe: (require typed/racket/unsafe) Using typed/rack… --- ## [Vulcan examples?](https://racket.discourse.group/t/vulcan-examples/3743)
**Author:** [@hendrikboom3](https://racket.discourse.group/u/hendrikboom3)\ **Replies:** 1\ **Last updated:** [May 15, 2025, 11:38pm UTC](https://racket.discourse.group/t/vulcan-examples/3743 "2025-05-15T23:38:48Z")
There is a Vulcan binding for Racket, documented here. In section 5.1 it explains that Right now the project has a strong need for example Vulkan applications. Has anyone written such examples? I've tried using the bi… --- ## [Racket v8.17 draft Release Notes](https://racket.discourse.group/t/racket-v8-17-draft-release-notes/3735)
**Author:** [@jbclements](https://racket.discourse.group/u/jbclements)\ **Replies:** 11\ **Last updated:** [May 15, 2025, 1:58pm UTC](https://racket.discourse.group/t/racket-v8-17-draft-release-notes/3735 "2025-05-15T13:58:58Z")
Here are the current draft release notes, let me know about things that are incorrect or missing! The package manager computes checksums for packages when required, allowing the use and automatic upgrade of packages … --- ## [Previous value of a syntax parameter? / block with non-local exits](https://racket.discourse.group/t/previous-value-of-a-syntax-parameter-block-with-non-local-exits/3741)
**Author:** [@soegaard](https://racket.discourse.group/u/soegaard)\ **Replies:** 10\ **Last updated:** [May 14, 2025, 1:24pm UTC](https://racket.discourse.group/t/previous-value-of-a-syntax-parameter-block-with-non-local-exits/3741 "2025-05-14T13:24:04Z")
Previous value a syntax parameter The block form from ISLisp Recently I came across the specification of ISLisp. What Scheme is to Racket, ISLisp is to Common Lisp. That is, the ISLisp specification is closer in style … --- ## [Testing for the v8.17 release](https://racket.discourse.group/t/testing-for-the-v8-17-release/3698)
**Author:** [@jbclements](https://racket.discourse.group/u/jbclements)\ **Replies:** 15\ **Last updated:** [May 13, 2025, 4:31pm UTC](https://racket.discourse.group/t/testing-for-the-v8-17-release/3698 "2025-05-13T16:31:13Z")
Testing for the v8.17 release (using the v8.16.900 release candidate build) Search for your name on the checklist page to find relevant items, either reply when you finish an item (please indicate which item/s is/are d… --- ## [Operator (from racket/base) not known](https://racket.discourse.group/t/operator-from-racket-base-not-known/3733)
**Author:** [@damien\_mattei](https://racket.discourse.group/u/damien_mattei)\ **Replies:** 2\ **Last updated:** [May 12, 2025, 10:04pm UTC](https://racket.discourse.group/t/operator-from-racket-base-not-known/3733 "2025-05-12T22:04:39Z")
Hi, i'm writing a parser to evaluate super-scripted expression (not sure it is a good idea in real life but i like the display) used in exponentiation expressions, here is a working example : Welcome to DrRacket, versi… --- ## [How do i test my language](https://racket.discourse.group/t/how-do-i-test-my-language/3739)
**Author:** [@Mrdev88](https://racket.discourse.group/u/Mrdev88)\ **Replies:** 3\ **Last updated:** [May 12, 2025, 4:54pm UTC](https://racket.discourse.group/t/how-do-i-test-my-language/3739 "2025-05-12T16:54:57Z")
I made a language in racket and i don't know how to test it Here's my directory: langtest/ lang/ reader.rkt main.rkt --- ## [Rhombus Documentation](https://racket.discourse.group/t/rhombus-documentation/3740)
**Author:** [@ShalokShalom](https://racket.discourse.group/u/ShalokShalom)\ **Replies:** 3\ **Last updated:** [May 12, 2025, 2:53pm UTC](https://racket.discourse.group/t/rhombus-documentation/3740 "2025-05-12T14:53:32Z")
Hi wonderful people :waving\_hand: Does the documentation generator need a dedicated Racket --\> Rhombus translation in the background, or can it create the existing documentation with the present tools? Considering that… --- ## [Boston Racket Meet-up May 10, 2025](https://racket.discourse.group/t/boston-racket-meet-up-may-10-2025/3717)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 9\ **Last updated:** [May 8, 2025, 6:43pm UTC](https://racket.discourse.group/t/boston-racket-meet-up-may-10-2025/3717 "2025-05-08T18:43:14Z")
Boston Racket Meet-up May 10 at 1pm, Room 366, PRL, Khoury College of Computer Sciences, Northeastern University, Boston (Diagonally across the street from the Museum of Fine Arts.) Take the elevators opposite the bi… --- ## [Cross compiling to a Raspberry Pi](https://racket.discourse.group/t/cross-compiling-to-a-raspberry-pi/3729)
**Author:** [@notjack](https://racket.discourse.group/u/notjack)\ **Replies:** 1\ **Last updated:** [May 7, 2025, 6:18pm UTC](https://racket.discourse.group/t/cross-compiling-to-a-raspberry-pi/3729 "2025-05-07T18:18:06Z")
Has anyone managed to get raco cross working with a Raspberry Pi? Specifically, I have a Racket package and I'd like to take that package's main.rkt file and demodularize it, cross-compile it to an executable for 64-bit … --- ## [Why are contracts not procedures?](https://racket.discourse.group/t/why-are-contracts-not-procedures/3727)
**Author:** [@joskoot](https://racket.discourse.group/u/joskoot)\ **Replies:** 2\ **Last updated:** [May 7, 2025, 7:13am UTC](https://racket.discourse.group/t/why-are-contracts-not-procedures/3727 "2025-05-07T07:13:14Z")
We have: (procedure? (-\> any/c any/c)) ; -\> #f (contract? (-\> any/c any/c)) ; -\> #t (contract? (λ (x) #t)) ; -\> #t Every procedure satisfying contract (-\> any/c any(c) is accepted as a contract, but the reverse is not … --- ## [C(a|d)ⁿr 1.1: Future-proofing RacketCon](https://racket.discourse.group/t/c-a-d-r-1-1-future-proofing-racketcon/3715)
**Author:** [@Eutro](https://racket.discourse.group/u/Eutro)\ **Replies:** 1\ **Last updated:** [May 4, 2025, 11:09pm UTC](https://racket.discourse.group/t/c-a-d-r-1-1-future-proofing-racketcon/3715 "2025-05-04T23:09:44Z")
With (fifteenth RacketCon) coming up, we will once again be running out of list accessors in racket/list soon. Fortunately, with the new c(a|d)ⁿr release now providing list accessors into the millions and beyond, this pr… --- ## [RacketCon 2025: Call for Presentations](https://racket.discourse.group/t/racketcon-2025-call-for-presentations/3718)
**Author:** [@bogdan](https://racket.discourse.group/u/bogdan)\ **Replies:** 0\ **Last updated:** [May 4, 2025, 4:40am UTC](https://racket.discourse.group/t/racketcon-2025-call-for-presentations/3718 "2025-05-04T04:40:55Z")
The RacketCon organizing committee is proud to announce the 2025 edition of RacketCon! The fifteenth RacketCon will take place at UMass Boston in Boston, Massachusetts, USA on October 4-5, 2025. RacketCon is a public… --- ## [Spring Lisp Game Jam 2025](https://racket.discourse.group/t/spring-lisp-game-jam-2025/3716)
**Author:** [@hendrikboom3](https://racket.discourse.group/u/hendrikboom3)\ **Replies:** 0\ **Last updated:** [May 3, 2025, 5:46pm UTC](https://racket.discourse.group/t/spring-lisp-game-jam-2025/3716 "2025-05-03T17:46:05Z")
There's another Lisp game jam coming up next month. See Spring Lisp Game Jam 2025 - itch.io for details. --- ## [Syntax Colours for Custom Dispatch Macros](https://racket.discourse.group/t/syntax-colours-for-custom-dispatch-macros/3714)
**Author:** [@bakgatviooldoos](https://racket.discourse.group/u/bakgatviooldoos)\ **Replies:** 0\ **Last updated:** [May 3, 2025, 9:22am UTC](https://racket.discourse.group/t/syntax-colours-for-custom-dispatch-macros/3714 "2025-05-03T09:22:58Z")
Hi, Racket Discourse. I wanted to try my hand at writing a reader macro extension, which was less intimidating than I thought it would be. The result works, but I am curious where I would implement custom syntax colour… --- ## [Repl delays, background CPU](https://racket.discourse.group/t/repl-delays-background-cpu/3684)
**Author:** [@acarrico](https://racket.discourse.group/u/acarrico)\ **Replies:** 9\ **Last updated:** [May 3, 2025, 2:40am UTC](https://racket.discourse.group/t/repl-delays-background-cpu/3684 "2025-05-03T02:40:21Z")
I've noticed some REPL issues. User perceptible delay and 100%CPU usage (two different issues). See below: In emacs / racket-mode: racket-mode\> (let loop () (define form (read)) (unless (eq? form 'q) (println form) (lo… --- ## [Picayune pict documentation details](https://racket.discourse.group/t/picayune-pict-documentation-details/3711)
**Author:** [@hendrikboom3](https://racket.discourse.group/u/hendrikboom3)\ **Replies:** 2\ **Last updated:** [May 1, 2025, 5:35pm UTC](https://racket.discourse.group/t/picayune-pict-documentation-details/3711 "2025-05-01T17:35:50Z")
In 2 Basic Pict Constructors it says The arguments to the rendering procedure will be a drawing context and top-left location for drawing. But it doesn't explain that 'draw' is the rendering procedure. And it's confu… --- ## [Is defining a function inside a loop without time penalty?](https://racket.discourse.group/t/is-defining-a-function-inside-a-loop-without-time-penalty/3392)
**Author:** [@damien\_mattei](https://racket.discourse.group/u/damien_mattei)\ **Replies:** 16\ **Last updated:** [April 29, 2025, 3:15pm UTC](https://racket.discourse.group/t/is-defining-a-function-inside-a-loop-without-time-penalty/3392 "2025-04-29T15:15:37Z")
hello, i have a for/list that contains some computation, a simple mathematic expression, that should only be used in the for/lisp loop , so i can define it in the for/lisp body but i'm asking if the defined function wil… --- ## [DrRacket setup for learning The Little Schemer](https://racket.discourse.group/t/drracket-setup-for-learning-the-little-schemer/3705)
**Author:** [@code2018](https://racket.discourse.group/u/code2018)\ **Replies:** 3\ **Last updated:** [April 28, 2025, 5:06pm UTC](https://racket.discourse.group/t/drracket-setup-for-learning-the-little-schemer/3705 "2025-04-28T17:06:48Z")
As the title says - are there links/docs to the basic setup as I would like to get started on the book (which I have been planning for a while) --- ## [Racket meet-up: Saturday, 3 May 2025](https://racket.discourse.group/t/racket-meet-up-saturday-3-may-2025/3704)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 0\ **Last updated:** [April 27, 2025, 11:33am UTC](https://racket.discourse.group/t/racket-meet-up-saturday-3-may-2025/3704 "2025-04-27T11:33:45Z")
Everyone is welcome to join us for the :racket: Racket meet-up: Saturday, 3 May 2025 at 18:00 UTC In your timezone: 2025-05-03T18:00:00Z (UTC). (converter). At this meet-up: Racket Meet-up Boston! RacketCon2025 Book … --- ## [Question about syntax](https://racket.discourse.group/t/question-about-syntax/3697)
**Author:** [@damien\_mattei](https://racket.discourse.group/u/damien_mattei)\ **Replies:** 4\ **Last updated:** [April 21, 2025, 8:07pm UTC](https://racket.discourse.group/t/question-about-syntax/3697 "2025-04-21T20:07:50Z")
Hi, i have this code : ;; operators (cond ((char=? c #\\+) (define n (string-\>number p-tok)) ; partial token is completed (if n (return (cons n (cons #'+ (parse-superscript-tok… --- ## [Can Typed Racket Treat Types as Runtime Values?](https://racket.discourse.group/t/can-typed-racket-treat-types-as-runtime-values/3696)
**Author:** [@NoahStoryM](https://racket.discourse.group/u/NoahStoryM)\ **Replies:** 0\ **Last updated:** [April 20, 2025, 4:34am UTC](https://racket.discourse.group/t/can-typed-racket-treat-types-as-runtime-values/3696 "2025-04-20T04:34:05Z")
I want to refine types without relying on predicates, so I attempted to implement ⊔, ann\* and type-case. Here are usage examples of these operators: (: flexible-length (→ (⊔ String (Listof Any)) Index)) (define (flexibl… --- ## [Game of Life using math/array](https://racket.discourse.group/t/game-of-life-using-math-array/584)
**Author:** [@alexh](https://racket.discourse.group/u/alexh)\ **Replies:** 4\ **Last updated:** [April 19, 2025, 6:39pm UTC](https://racket.discourse.group/t/game-of-life-using-math-array/584 "2025-04-19T18:39:57Z")
Since the use of math/array came up recently in a topic here, I thought, I'll have a look at the package and see how difficult it would be to implement the game of life (Conway's Game of Life - Wikipedia) using it. Turn… --- ## [Exporting a struct invariant contract](https://racket.discourse.group/t/exporting-a-struct-invariant-contract/3694)
**Author:** [@KevinW](https://racket.discourse.group/u/KevinW)\ **Replies:** 2\ **Last updated:** [April 18, 2025, 10:23pm UTC](https://racket.discourse.group/t/exporting-a-struct-invariant-contract/3694 "2025-04-18T22:23:45Z")
Hi, I'm trying to create a struct with a contract that involves a relationship between two fields. The struct needs to be exported. It seems like what I need is an "invariant contract" as in struct/dc: 8.1 Data-structur… [Previous page](https://racket.discourse.group/latest.md?page=13) [Next page](https://racket.discourse.group/latest.md?page=15)