# Latest **URL:** https://racket.discourse.group/latest.md?page=49 [Latest](https://racket.discourse.group/latest.md) · [Categories](https://racket.discourse.group/categories.md) · [Tags](https://racket.discourse.group/tags.md) **Page:** 50 --- ## [Writing a simple interpreter which can add numbers in tree form](https://racket.discourse.group/t/writing-a-simple-interpreter-which-can-add-numbers-in-tree-form/1668)
**Author:** [@devosalain](https://racket.discourse.group/u/devosalain)\ **Replies:** 4\ **Last updated:** [January 29, 2023, 8:42pm UTC](https://racket.discourse.group/t/writing-a-simple-interpreter-which-can-add-numbers-in-tree-form/1668 "2023-01-29T20:42:00Z")
Following code works perfect: #lang typed/racket (require racket/match ) (define-struct myoperand (\[ O : \[U 'plus 'minus\] \])) (define-struct myleaf (\[ L : Number\])) (define-struct mynode (\[ N :(cons myoperand (co… --- ## [Fighting with racket type-system & match](https://racket.discourse.group/t/fighting-with-racket-type-system-match/1669)
**Author:** [@devosalain](https://racket.discourse.group/u/devosalain)\ **Replies:** 1\ **Last updated:** [January 28, 2023, 1:55pm UTC](https://racket.discourse.group/t/fighting-with-racket-type-system-match/1669 "2023-01-28T13:55:58Z")
Following program defines 3 types and one function which tries to match the 3 types. The error given is : "match syntax error in pattern in : (stc x) Obvious question why ? #lang typed/racket (require racket/match )… --- ## [Multiple values with Racket behave different than Guile or Chicken](https://racket.discourse.group/t/multiple-values-with-racket-behave-different-than-guile-or-chicken/1667)
**Author:** [@damien\_mattei](https://racket.discourse.group/u/damien_mattei)\ **Replies:** 5\ **Last updated:** [January 28, 2023, 9:25am UTC](https://racket.discourse.group/t/multiple-values-with-racket-behave-different-than-guile-or-chicken/1667 "2023-01-28T09:25:20Z")
hello, it is for a while i did not use 'values in Scheme and i did not use often 'values (so i perhaps have a problem of comprehension with 'values) and doing this in Racket with racket language or R5RS give the same er… --- ## [Where are GLU and GLUT libraries for OpenGL?](https://racket.discourse.group/t/where-are-glu-and-glut-libraries-for-opengl/1657)
**Author:** [@hendrikboom3](https://racket.discourse.group/u/hendrikboom3)\ **Replies:** 5\ **Last updated:** [January 27, 2023, 9:46pm UTC](https://racket.discourse.group/t/where-are-glu-and-glut-libraries-for-opengl/1657 "2023-01-27T21:46:56Z")
Is there a Racket-style GLU to go with sgl, the Racket-style OpenGL? Same for any other traditional helper libraries? (GLUT?) I have not been able to guess the proper spelling of gluPerspective in Racket-style. glu-p… --- ## [Provide an example using "eval-syntax" & "syntax" in typed/racket](https://racket.discourse.group/t/provide-an-example-using-eval-syntax-syntax-in-typed-racket/1662)
**Author:** [@devosalain](https://racket.discourse.group/u/devosalain)\ **Replies:** 7\ **Last updated:** [January 26, 2023, 12:35am UTC](https://racket.discourse.group/t/provide-an-example-using-eval-syntax-syntax-in-typed-racket/1662 "2023-01-26T00:35:47Z")
I have difficulty using typed/racket & the function "eval-syntax". Can someone provide a compiling example --- ## [When would you use language plait & when would you use language typed/racket?](https://racket.discourse.group/t/when-would-you-use-language-plait-when-would-you-use-language-typed-racket/1663)
**Author:** [@devosalain](https://racket.discourse.group/u/devosalain)\ **Replies:** 9\ **Last updated:** [January 27, 2023, 5:15am UTC](https://racket.discourse.group/t/when-would-you-use-language-plait-when-would-you-use-language-typed-racket/1663 "2023-01-27T05:15:00Z")
When would you use language plait & when would you use language typed/racket ? --- ## [Language plait and gui](https://racket.discourse.group/t/language-plait-and-gui/1666)
**Author:** [@devosalain](https://racket.discourse.group/u/devosalain)\ **Replies:** 5\ **Last updated:** [January 27, 2023, 3:23am UTC](https://racket.discourse.group/t/language-plait-and-gui/1666 "2023-01-27T03:23:51Z")
Is it possible to run a gui when the language is plait. Following code fails ;#lang racket #lang plait (require racket/gui) (require racket/class) (define window (new frame% \[label "Hello World!"\])) (send wind… --- ## [Call by reference](https://racket.discourse.group/t/call-by-reference/1665)
**Author:** [@devosalain](https://racket.discourse.group/u/devosalain)\ **Replies:** 1\ **Last updated:** [January 27, 2023, 12:30am UTC](https://racket.discourse.group/t/call-by-reference/1665 "2023-01-27T00:30:28Z")
What do you think of following demo code demostrating call-by-reference. #lang typed/racket ( : addone : \[Boxof Integer\] -\> Void ) (define addone (lambda (x) \[begin (: ux : Integer ) (define ux (unbo… --- ## [Using (string-downcase ...) makes (eq? ...) fail](https://racket.discourse.group/t/using-string-downcase-makes-eq-fail/1664)
**Author:** [@Grafcube](https://racket.discourse.group/u/Grafcube)\ **Replies:** 1\ **Last updated:** [January 26, 2023, 2:21pm UTC](https://racket.discourse.group/t/using-string-downcase-makes-eq-fail/1664 "2023-01-26T14:21:58Z")
I have these functions here (define (greetfmt name) (string-append "Hello " name "!")) (define (auth? name) (or (eq? name "alice") (eq? name "bob"))) (define (greet name) ;;(if (auth? name) (if (auth? (str… --- ## [User config files](https://racket.discourse.group/t/user-config-files/1659)
**Author:** [@joeld](https://racket.discourse.group/u/joeld)\ **Replies:** 4\ **Last updated:** [January 24, 2023, 6:43pm UTC](https://racket.discourse.group/t/user-config-files/1659 "2023-01-24T18:43:38Z")
Does anyone have a favorite cross-platform method for storing/retrieving per-user configuration options for their apps? I can’t find it now, so I may have hallucinated it, but I thought I remembered seeing some function… --- ## [\[Newbie\] How to improve my terrible calculator?](https://racket.discourse.group/t/newbie-how-to-improve-my-terrible-calculator/1654)
**Author:** [@JohnSnow](https://racket.discourse.group/u/JohnSnow)\ **Replies:** 2\ **Last updated:** [January 23, 2023, 8:48am UTC](https://racket.discourse.group/t/newbie-how-to-improve-my-terrible-calculator/1654 "2023-01-23T08:48:42Z")
I am slightly past the "beginning student language" and I am trying to implement a simple calculator with what I have learned. However, I feel the code can be shorter and simpler but I don't know how. What's a better way… --- ## [Proposed stable branch discipline](https://racket.discourse.group/t/proposed-stable-branch-discipline/1453)
**Author:** [@jbclements](https://racket.discourse.group/u/jbclements)\ **Replies:** 7\ **Last updated:** [January 20, 2023, 7:07pm UTC](https://racket.discourse.group/t/proposed-stable-branch-discipline/1453 "2023-01-20T19:07:09Z")
Following discussion with @elibarzilay and @LiberalArtist , I think we're proposing a slightly revised discipline on the handling of the stable branch. Specifically, here are two excerpts from the release checklist: At … --- ## [Racket FAQ: images outside of DrRacket and does the list of questions need updating?](https://racket.discourse.group/t/racket-faq-images-outside-of-drracket-and-does-the-list-of-questions-need-updating/1651)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 0\ **Last updated:** [January 20, 2023, 3:58pm UTC](https://racket.discourse.group/t/racket-faq-images-outside-of-drracket-and-does-the-list-of-questions-need-updating/1651 "2023-01-20T15:58:20Z")
Just a little thing, but someone asked how they could display images if they weren't using DrRacket. ▶ Note It's not the first time someone has asked so I added 'How do I display images outside of DrRacket?' to the Racke… --- ## [Racket v8.8 Release Thread](https://racket.discourse.group/t/racket-v8-8-release-thread/1614)
**Author:** [@jbclements](https://racket.discourse.group/u/jbclements)\ **Replies:** 3\ **Last updated:** [January 20, 2023, 6:47am UTC](https://racket.discourse.group/t/racket-v8-8-release-thread/1614 "2023-01-20T06:47:40Z")
The release process for v8.8 will begin in about a week. 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. Upcoming dates: - 9th: Branch day, merge… --- ## [Is \`(unsafe-struct\*-ref s -1)\` a stable way to get type descriptors in Racket?](https://racket.discourse.group/t/is-unsafe-struct-ref-s-1-a-stable-way-to-get-type-descriptors-in-racket/1646)
**Author:** [@MartianMoorGrove](https://racket.discourse.group/u/MartianMoorGrove)\ **Replies:** 6\ **Last updated:** [January 20, 2023, 12:59am UTC](https://racket.discourse.group/t/is-unsafe-struct-ref-s-1-a-stable-way-to-get-type-descriptors-in-racket/1646 "2023-01-20T00:59:37Z")
By stable I mean that the location of struct type descriptors within struct instances is, within reason, a permanent feature of the language. Obviously on it's own that code is both unsafe and useless on impersonators, … --- ## [Blog with Metapict examples](https://racket.discourse.group/t/blog-with-metapict-examples/1645)
**Author:** [@soegaard](https://racket.discourse.group/u/soegaard)\ **Replies:** 3\ **Last updated:** [January 19, 2023, 2:16pm UTC](https://racket.discourse.group/t/blog-with-metapict-examples/1645 "2023-01-19T14:16:54Z")
Hi All. I decided to write a "blog" where the theme is drawing figures with Metapict. The first four entries are Arrows Regular Polygons Venn Diagrams Simple Block Diagrams Comments are welcome. https://soegaard.gi… --- ## [Reactions plugin?](https://racket.discourse.group/t/reactions-plugin/1635)
**Author:** [@jbclements](https://racket.discourse.group/u/jbclements)\ **Replies:** 7\ **Last updated:** [January 18, 2023, 6:22pm UTC](https://racket.discourse.group/t/reactions-plugin/1635 "2023-01-18T18:22:14Z")
enabling this (officially supported) plugin, I'll turn it off if people object? --- ## [Does anyone know of a working implementation of the ActivityPub protocol in Racket?](https://racket.discourse.group/t/does-anyone-know-of-a-working-implementation-of-the-activitypub-protocol-in-racket/1571)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 7\ **Last updated:** [January 18, 2023, 2:20pm UTC](https://racket.discourse.group/t/does-anyone-know-of-a-working-implementation-of-the-activitypub-protocol-in-racket/1571 "2023-01-18T14:20:27Z")
Does anyone know of a working implementation of the ActivityPub protocol in Racket? s. --- ## [Macro Output Spliced into Context](https://racket.discourse.group/t/macro-output-spliced-into-context/1641)
**Author:** [@Liam.Gaudy](https://racket.discourse.group/u/Liam.Gaudy)\ **Replies:** 9\ **Last updated:** [January 17, 2023, 5:13pm UTC](https://racket.discourse.group/t/macro-output-spliced-into-context/1641 "2023-01-17T17:13:07Z")
I was just about to give up on doing the below, when I thought it might be fun for a more experienced person to offer advice. I have this repetitive cond for a comparator, with my thanks to @notjack for writing such impo… --- ## [Set input text box scroll position? (gui-easy)](https://racket.discourse.group/t/set-input-text-box-scroll-position-gui-easy/1638)
**Author:** [@joeld](https://racket.discourse.group/u/joeld)\ **Replies:** 5\ **Last updated:** [January 16, 2023, 4:39pm UTC](https://racket.discourse.group/t/set-input-text-box-scroll-position-gui-easy/1638 "2023-01-16T16:39:52Z")
I’m creating my first GUI app, and I want to use input (from gui-easy) to display the output of a long-running command in "real time" (i.e. not waiting until the command is finished). When the output has more lines than … --- ## [Two new Racket Cookbooks: Slideshow and scribble](https://racket.discourse.group/t/two-new-racket-cookbooks-slideshow-and-scribble/1640)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 0\ **Last updated:** [January 16, 2023, 2:06pm UTC](https://racket.discourse.group/t/two-new-racket-cookbooks-slideshow-and-scribble/1640 "2023-01-16T14:06:56Z")
Racket Cookbooks now include two new cookbooks Slideshow and scribble Plot Cookbook - lots of pretty plots GUI Cookbook - all examples work on Linux, Windows and macOS Rsound Cookbook - this is a work in progress S… --- ## [Discourse Chat!](https://racket.discourse.group/t/discourse-chat/1639)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 0\ **Last updated:** [January 14, 2023, 6:47pm UTC](https://racket.discourse.group/t/discourse-chat/1639 "2023-01-14T18:47:16Z")
Racket Discourse now has chat! Why? Sometime you want to chat without generating a bunch of messages for mailing list mode users, and not everyone has or wants an account on discord, Slack, telegram, WhatsApp, etc. T… --- ## [Generating svgs using the html renderer for Scribble](https://racket.discourse.group/t/generating-svgs-using-the-html-renderer-for-scribble/1634)
**Author:** [@soegaard](https://racket.discourse.group/u/soegaard)\ **Replies:** 2\ **Last updated:** [January 11, 2023, 9:14pm UTC](https://racket.discourse.group/t/generating-svgs-using-the-html-renderer-for-scribble/1634 "2023-01-11T21:14:02Z")
Hi All, The the html renderer for Scribble has a keyword argument #:image-preferences. The argument can be used to pass a list of preferred image formats to Scribble, such as svg, png etc. In the example program belo… --- ## [Installing Racket from package repositories](https://racket.discourse.group/t/installing-racket-from-package-repositories/1630)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 5\ **Last updated:** [January 12, 2023, 4:18pm UTC](https://racket.discourse.group/t/installing-racket-from-package-repositories/1630 "2023-01-12T16:18:43Z")
Hi, A problem new users sometimes run into is they install an old version of Racket (or minimal racket) from package repositories. (see Racket Packaging Status below) I was reading about Helix Editor and I noticed that… --- ## [You are invited to the First Congress for Attribution-Based Economics!](https://racket.discourse.group/t/you-are-invited-to-the-first-congress-for-attribution-based-economics/1566)
**Author:** [@countvajhula](https://racket.discourse.group/u/countvajhula)\ **Replies:** 1\ **Last updated:** [January 11, 2023, 8:29pm UTC](https://racket.discourse.group/t/you-are-invited-to-the-first-congress-for-attribution-based-economics/1566 "2023-01-11T20:29:01Z")
(crossposted to Emacs Reddit) Dear friends, Following up on my recent talk at EmacsConf (youtube| toobnix| Q&A), we are prototyping a new economic system in the open source community, and your participation is essentia… --- ## [Snippets in DrRacket?](https://racket.discourse.group/t/snippets-in-drracket/1633)
**Author:** [@Panadestein](https://racket.discourse.group/u/Panadestein)\ **Replies:** 2\ **Last updated:** [January 11, 2023, 6:40pm UTC](https://racket.discourse.group/t/snippets-in-drracket/1633 "2023-01-11T18:40:36Z")
Maybe I am missing something in the DrRacket workflow, but I find this to be a very useful feature in any text editor. I have been googling for a while, and I haven't found an answer for this. With snippets, I mean code… --- ## [Description of Racket Distribution for download and package repo pages?](https://racket.discourse.group/t/description-of-racket-distribution-for-download-and-package-repo-pages/1608)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 24\ **Last updated:** [January 10, 2023, 7:28pm UTC](https://racket.discourse.group/t/description-of-racket-distribution-for-download-and-package-repo-pages/1608 "2023-01-10T19:28:19Z")
I think I’ve gone mad but I thought we had a summary of what was in the Racket distribution somewhere on https://racket-lang.org ? @capfredf has kindly created a package for flathub, but it makes me think the lack of a… --- ## [Why is plot slower with unicode symbols in ticks?](https://racket.discourse.group/t/why-is-plot-slower-with-unicode-symbols-in-ticks/1611)
**Author:** [@benknoble](https://racket.discourse.group/u/benknoble)\ **Replies:** 25\ **Last updated:** [January 10, 2023, 3:44pm UTC](https://racket.discourse.group/t/why-is-plot-slower-with-unicode-symbols-in-ticks/1611 "2023-01-10T15:44:52Z")
I have some plot code for dice statistics (unfinished). It seems from some observations that using unicode characters in the y-axis ticks makes the plot nearly unresponsive. Conversely, using ASCII-only characters has no… --- ## [Places parallelism -- how to return ASAP after 1st answer](https://racket.discourse.group/t/places-parallelism-how-to-return-asap-after-1st-answer/1626)
**Author:** [@rscho](https://racket.discourse.group/u/rscho)\ **Replies:** 3\ **Last updated:** [January 9, 2023, 2:36pm UTC](https://racket.discourse.group/t/places-parallelism-how-to-return-asap-after-1st-answer/1626 "2023-01-09T14:36:27Z")
Hi, Taking the example program for places from the docs: (let (\[pls (for/list (\[i (in-range 2)\]) (dynamic-place "place-worker.rkt" 'place-main))\]) (for (\[i (in-range 2)\] \[p pls\]) (place-… --- ## [Usage of code-examples in scribble](https://racket.discourse.group/t/usage-of-code-examples-in-scribble/1628)
**Author:** [@Panadestein](https://racket.discourse.group/u/Panadestein)\ **Replies:** 4\ **Last updated:** [January 9, 2023, 12:13am UTC](https://racket.discourse.group/t/usage-of-code-examples-in-scribble/1628 "2023-01-09T00:13:56Z")
Hello everyone, I have been recently working on SICP with Chez Scheme. I was using Emacs with org-mode to organize my solutions using literate programming, and then exporting them to HTML. Then I read about Racket, DrR… [Previous page](https://racket.discourse.group/latest.md?page=48) [Next page](https://racket.discourse.group/latest.md?page=50)