# Questions & Answers **URL:** https://racket.discourse.group/c/questions/6.md?page=2 [Latest](https://racket.discourse.group/latest.md) · [Categories](https://racket.discourse.group/categories.md) · [Tags](https://racket.discourse.group/tags.md) **Page:** 3 --- ## [Javascript module causes error in DrRacket](https://racket.discourse.group/t/javascript-module-causes-error-in-drracket/4097)
**Author:** [@nealburns5](https://racket.discourse.group/u/nealburns5)\ **Replies:** 16\ **Last updated:** [February 4, 2026, 1:16pm UTC](https://racket.discourse.group/t/javascript-module-causes-error-in-drracket/4097 "2026-02-04T13:16:32Z")
Hi, If I install the javascript module, I get the error below every time I start DrRacket. It happens in windows and linux running under WSL. Thanks, Neal Error invoking tool #\ **Author:** [@pavpanchekha](https://racket.discourse.group/u/pavpanchekha)\ **Replies:** 6\ **Last updated:** [February 3, 2026, 4:00pm UTC](https://racket.discourse.group/t/virtualenv-like-installation/4089 "2026-02-03T16:00:21Z") I have multiple repos on my computer that require different / incompatible versions of a library. (Because I develop both the clients and the library and sometimes need to make coordinated changes.) It's a pain to switch… --- ## [Continuations issue - Shift vs Control](https://racket.discourse.group/t/continuations-issue-shift-vs-control/4083)
**Author:** [@matteo-daddio](https://racket.discourse.group/u/matteo-daddio)\ **Replies:** 4\ **Last updated:** [January 31, 2026, 12:40pm UTC](https://racket.discourse.group/t/continuations-issue-shift-vs-control/4083 "2026-01-31T12:40:51Z")
Hello, I need to work with continuations. I read the documentation about it and is very well written. Only the documentation about the racket/control library is a bit cryptic. I needed to ask the AI for help and I think… --- ## [WeScheme errors, DrRacket happy](https://racket.discourse.group/t/wescheme-errors-drracket-happy/4094)
**Author:** [@maueroats](https://racket.discourse.group/u/maueroats)\ **Replies:** 4\ **Last updated:** [January 29, 2026, 5:03pm UTC](https://racket.discourse.group/t/wescheme-errors-drracket-happy/4094 "2026-01-29T17:03:11Z")
Run the animation below. Slowly move the mouse into the window from the bottom near the right. Get an error. Maxmimum call stack size exceeded I can't figure out what's wrong. Can anybody see the issue? Touching this… --- ## [Dynamic combo-field% behavior - filtering choices by typed text](https://racket.discourse.group/t/dynamic-combo-field-behavior-filtering-choices-by-typed-text/4093)
**Author:** [@lannydpittman](https://racket.discourse.group/u/lannydpittman)\ **Replies:** 1\ **Last updated:** [January 28, 2026, 9:03pm UTC](https://racket.discourse.group/t/dynamic-combo-field-behavior-filtering-choices-by-typed-text/4093 "2026-01-28T21:03:13Z")
Looking for a way to implement an 'auto-complete' for combo-field%. As the user types text into the combo-field%, the callback filters non-matching text options from the list and add faded 'tab-complete' text after the… --- ## [Requesting help to translate small array program into typed racket](https://racket.discourse.group/t/requesting-help-to-translate-small-array-program-into-typed-racket/4079)
**Author:** [@Gambiteer](https://racket.discourse.group/u/Gambiteer)\ **Replies:** 10\ **Last updated:** [January 25, 2026, 6:38pm UTC](https://racket.discourse.group/t/requesting-help-to-translate-small-array-program-into-typed-racket/4079 "2026-01-25T18:38:32Z")
When I added array broadcasting to SRFI 231 here GitHub - gambiteer/srfi-231 at 231-bis I made some design decisions that differ from those in Racket's math/array and I would like to compare the implementations of the tw… --- ## [What happened to the polyglot package?](https://racket.discourse.group/t/what-happened-to-the-polyglot-package/4080)
**Author:** [@ToddOBryan](https://racket.discourse.group/u/ToddOBryan)\ **Replies:** 3\ **Last updated:** [January 15, 2026, 11:57pm UTC](https://racket.discourse.group/t/what-happened-to-the-polyglot-package/4080 "2026-01-15T23:57:26Z")
All links go to nothing. Did it get dropped? Also, and possibly better as another question is there a discussion group or list for Pollen? I'm making a website and want to look at old questions/best practices. --- ## [How does \_array/list work?](https://racket.discourse.group/t/how-does-array-list-work/4078)
**Author:** [@MickeyKnox](https://racket.discourse.group/u/MickeyKnox)\ **Replies:** 7\ **Last updated:** [January 15, 2026, 10:40pm UTC](https://racket.discourse.group/t/how-does-array-list-work/4078 "2026-01-15T22:40:11Z")
I have a list that I want to convert into a C array. \_array/list looks promising, as "the Racket representation is a list". But how exactly can I convert my list into a C array? --- ## [Trying to create my perfect Racket for AP CS Principles - will someone take pity?](https://racket.discourse.group/t/trying-to-create-my-perfect-racket-for-ap-cs-principles-will-someone-take-pity/4012)
**Author:** [@ToddOBryan](https://racket.discourse.group/u/ToddOBryan)\ **Replies:** 15\ **Last updated:** [January 15, 2026, 7:31am UTC](https://racket.discourse.group/t/trying-to-create-my-perfect-racket-for-ap-cs-principles-will-someone-take-pity/4012 "2026-01-15T07:31:08Z")
So, to review, I'm teaching AP CSP. About 40% of the course is supposed to cover programming and algorithms, and they publish their own pseudocode language, since the language the course is taught in is left to the instr… --- ## [Trouble with submodules](https://racket.discourse.group/t/trouble-with-submodules/4077)
**Author:** [@rvdalen](https://racket.discourse.group/u/rvdalen)\ **Replies:** 9\ **Last updated:** [January 13, 2026, 5:26pm UTC](https://racket.discourse.group/t/trouble-with-submodules/4077 "2026-01-13T17:26:28Z")
Hi, I am having some trouble with submodules. The following short program gives an error in DrRacket 9.0: #lang racket/base (require 'bar) (define (foo) "foo") (module bar racket/base (provide bar) (define (b… --- ## [Any chance at more abstraction with \`Values\` type?](https://racket.discourse.group/t/any-chance-at-more-abstraction-with-values-type/4057)
**Author:** [@wilbowma](https://racket.discourse.group/u/wilbowma)\ **Replies:** 9\ **Last updated:** [January 5, 2026, 4:55pm UTC](https://racket.discourse.group/t/any-chance-at-more-abstraction-with-values-type/4057 "2026-01-05T16:55:54Z")
I was writing a little library that uses multiple return values, and decided to port it to Typed Racket as some of the invariants were getting fiddly. However, due to limitations in the Values, I can't type the pattern I… --- ## [为什么 raco 不能自动更新 racket？\[Why can't I update racket by raco?\]](https://racket.discourse.group/t/raco-racket-why-cant-i-update-racket-by-raco/4071)
**Author:** [@litjohn](https://racket.discourse.group/u/litjohn)\ **Replies:** 2\ **Last updated:** [January 2, 2026, 2:51am UTC](https://racket.discourse.group/t/raco-racket-why-cant-i-update-racket-by-raco/4071 "2026-01-02T02:51:06Z")
rt。很好奇。\[I'm curious about it.\] --- ## [How to achieve zero-overhead type dispatch in macros (similar to C++ templates)?](https://racket.discourse.group/t/how-to-achieve-zero-overhead-type-dispatch-in-macros-similar-to-c-templates/4070)
**Author:** [@litjohn](https://racket.discourse.group/u/litjohn)\ **Replies:** 8\ **Last updated:** [January 1, 2026, 7:27pm UTC](https://racket.discourse.group/t/how-to-achieve-zero-overhead-type-dispatch-in-macros-similar-to-c-templates/4070 "2026-01-01T19:27:44Z")
Hi everyone! This is my first post here. I've been exploring Racket macros and have a question regarding performance and types. Is there a way in Racket to achieve zero-overhead type dispatch similar to C++ templates? … --- ## [Question about text in 2htdp/image teachpack](https://racket.discourse.group/t/question-about-text-in-2htdp-image-teachpack/4054)
**Author:** [@a-user](https://racket.discourse.group/u/a-user)\ **Replies:** 2\ **Last updated:** [December 24, 2025, 7:17am UTC](https://racket.discourse.group/t/question-about-text-in-2htdp-image-teachpack/4054 "2025-12-24T07:17:26Z")
In the documentation of text here, it says: The text size is measured in pixels, not points, so passing 24 to text should result in an image whose height is 24 (which might not be the case if the size were measured in p… --- ## [Using Redex as an interactive lambda-calculus workbench?](https://racket.discourse.group/t/using-redex-as-an-interactive-lambda-calculus-workbench/4053)
**Author:** [@msap](https://racket.discourse.group/u/msap)\ **Replies:** 1\ **Last updated:** [December 23, 2025, 3:26am UTC](https://racket.discourse.group/t/using-redex-as-an-interactive-lambda-calculus-workbench/4053 "2025-12-23T03:26:41Z")
I’m working through Lambda-Calculus and Combinators: An Introduction (Hindley & Seldin) and I’m looking for a locally installable Racket-based tool that can act as an interactive workbench for untyped lambda calculus an… --- ## [Running format procedure code example results in error](https://racket.discourse.group/t/running-format-procedure-code-example-results-in-error/4051)
**Author:** [@a-user](https://racket.discourse.group/u/a-user)\ **Replies:** 4\ **Last updated:** [December 22, 2025, 2:15pm UTC](https://racket.discourse.group/t/running-format-procedure-code-example-results-in-error/4051 "2025-12-22T14:15:20Z")
Typing one of the code example for format in DrRacket returns error. Racket version: 9.0 Language: BSL Documentation link: format Code: (format "the value of ~s is ~a" '(+ 1 1) (+ 1 1)) Error: quote: expected the na… --- ## [Pyffi with numpy (\<1.26) low-level lib and Python 3.1x](https://racket.discourse.group/t/pyffi-with-numpy-1-26-low-level-lib-and-python-3-1x/4036)
**Author:** [@damien\_mattei](https://racket.discourse.group/u/damien_mattei)\ **Replies:** 40\ **Last updated:** [December 15, 2025, 1:32pm UTC](https://racket.discourse.group/t/pyffi-with-numpy-1-26-low-level-lib-and-python-3-1x/4036 "2025-12-15T13:32:52Z")
Hi, I try to use pyffi but i have a Mac with Python 3.9 by default from Apple and Python 3.12 for work for depandancies with some scientific libraries. pyffi is searching for version 3.10 so i did: /Applications/Racket… --- ## [Pyffi: ref procedure](https://racket.discourse.group/t/pyffi-ref-procedure/4045)
**Author:** [@damien\_mattei](https://racket.discourse.group/u/damien_mattei)\ **Replies:** 4\ **Last updated:** [December 12, 2025, 4:24pm UTC](https://racket.discourse.group/t/pyffi-ref-procedure/4045 "2025-12-12T16:24:43Z")
Where does the ref procedure defined? i can not find it in the code ,nor in numpy or python and not in the documentation. It seems used to access a line like in an ndarray: (define Z (numpy.array '\[\[0 0 0 0 0 0\] … --- ## [Using a list as argument to a procedure which needs separate arguments -- "unwrapping a list"](https://racket.discourse.group/t/using-a-list-as-argument-to-a-procedure-which-needs-separate-arguments-unwrapping-a-list/4044)
**Author:** [@meijeru](https://racket.discourse.group/u/meijeru)\ **Replies:** 2\ **Last updated:** [December 12, 2025, 2:07pm UTC](https://racket.discourse.group/t/using-a-list-as-argument-to-a-procedure-which-needs-separate-arguments-unwrapping-a-list/4044 "2025-12-12T14:07:12Z")
I would like to have the procedures min/max work on LISTS of numbers rather than on a series of individual numbers. Thus: (min '\[3 1 2 0\]) = 0, where now I have to write (min 3 1 2 0). This is all fine for literal series… --- ## [Ordering relations between non-numbers](https://racket.discourse.group/t/ordering-relations-between-non-numbers/4040)
**Author:** [@meijeru](https://racket.discourse.group/u/meijeru)\ **Replies:** 2\ **Last updated:** [December 12, 2025, 1:26pm UTC](https://racket.discourse.group/t/ordering-relations-between-non-numbers/4040 "2025-12-12T13:26:43Z")
I would like to be able to compare two lists, strings, and in general sequences for their ordering: smaller than or greater than. I don't see a procedure for that in the current version. --- ## [Ansi colour output in drracket](https://racket.discourse.group/t/ansi-colour-output-in-drracket/4015)
**Author:** [@hendrikboom3](https://racket.discourse.group/u/hendrikboom3)\ **Replies:** 8\ **Last updated:** [December 9, 2025, 3:37pm UTC](https://racket.discourse.group/t/ansi-colour-output-in-drracket/4015 "2025-12-09T15:37:06Z")
I run the following in drracket: #lang racket/base (require ansi-color) (printf "plain text~n") (with-colors 'red (lambda () (printf "red text~n"))) (with-colors 'green (lambda () (printf "green text~n"))) In the outpu… --- ## [Stopping the main thread](https://racket.discourse.group/t/stopping-the-main-thread/4037)
**Author:** [@hendrikboom3](https://racket.discourse.group/u/hendrikboom3)\ **Replies:** 5\ **Last updated:** [December 3, 2025, 9:43pm UTC](https://racket.discourse.group/t/stopping-the-main-thread/4037 "2025-12-03T21:43:24Z")
My main thread sets up some GUI, and needs to cede the stage for the GUI to take over. I wrote #lang racket (require racket/gui/base) (require racket/class) (define my-canvas% (class canvas% ; The base class is canva… --- ## [Update and setup?](https://racket.discourse.group/t/update-and-setup/4032)
**Author:** [@joskoot](https://racket.discourse.group/u/joskoot)\ **Replies:** 0\ **Last updated:** [November 29, 2025, 10:49am UTC](https://racket.discourse.group/t/update-and-setup/4032 "2025-11-29T10:49:21Z")
I use 'do what I mean' in file/package manager of DrRacket after changing a github. Sometimes I see 'update', other times 'update and setup '. Both work. What is the difference between the two? ~~~~ --- ## [How to debug macros?](https://racket.discourse.group/t/how-to-debug-macros/4027)
**Author:** [@hendrikboom3](https://racket.discourse.group/u/hendrikboom3)\ **Replies:** 4\ **Last updated:** [November 27, 2025, 7:06pm UTC](https://racket.discourse.group/t/how-to-debug-macros/4027 "2025-11-27T19:06:21Z")
I get this message: . . ../../../../../usr/local/racket/collects/racket/private/kw.rkt:1263:25: application: not a procedure; expected a procedure that can be applied to arguments given: #\ It suggests to me th… --- ## ["Variadic" Lambda Calculus Abstractions](https://racket.discourse.group/t/variadic-lambda-calculus-abstractions/4021)
**Author:** [@bakgatviooldoos](https://racket.discourse.group/u/bakgatviooldoos)\ **Replies:** 4\ **Last updated:** [November 25, 2025, 9:39am UTC](https://racket.discourse.group/t/variadic-lambda-calculus-abstractions/4021 "2025-11-25T09:39:20Z")
Hi, Racket Discourse. I guess this is more of a theoretical question than a Racket question, per se, but the audience is well-placed, nonetheless. I am thinking about how one would implement "sugar" for variadic lambda… --- ## [Close a %frame programatically](https://racket.discourse.group/t/close-a-frame-programatically/4019)
**Author:** [@hendrikboom3](https://racket.discourse.group/u/hendrikboom3)\ **Replies:** 1\ **Last updated:** [November 22, 2025, 4:11pm UTC](https://racket.discourse.group/t/close-a-frame-programatically/4019 "2025-11-22T16:11:00Z")
How do I close a top-level %frame? Of course I can click on the close button the OS provides me at the top right corner. But what if the program I am running wants to initiate the close without user involvement? And t… --- ## [I cannot use SLLGEN on Racket 8.18: “collection not found: sllgen”](https://racket.discourse.group/t/i-cannot-use-sllgen-on-racket-8-18-collection-not-found-sllgen/4016)
**Author:** [@d1n0](https://racket.discourse.group/u/d1n0)\ **Replies:** 1\ **Last updated:** [November 20, 2025, 3:39pm UTC](https://racket.discourse.group/t/i-cannot-use-sllgen-on-racket-8-18-collection-not-found-sllgen/4016 "2025-11-20T15:39:29Z")
I'm trying to use SLLGEN in Racket 8.18, but it doesn't exist as a collection. require sllgen fails. raco pkg install fails due to SSL errors. What's the correct/current way to get SLLGEN in modern Racket? --- ## [Transparent Syntax Extensions](https://racket.discourse.group/t/transparent-syntax-extensions/4007)
**Author:** [@selfofly](https://racket.discourse.group/u/selfofly)\ **Replies:** 18\ **Last updated:** [November 20, 2025, 7:25am UTC](https://racket.discourse.group/t/transparent-syntax-extensions/4007 "2025-11-20T07:25:01Z")
Hello everyone! My question is: is there a way in Racket to implement transparent syntax extensions from inside the language? What I mean is I’d like to be able to (somehow) define a new syntax object of arbitrary form… --- ## [Cond-expand in Racket](https://racket.discourse.group/t/cond-expand-in-racket/4000)
**Author:** [@damien\_mattei](https://racket.discourse.group/u/damien_mattei)\ **Replies:** 9\ **Last updated:** [November 14, 2025, 6:48pm UTC](https://racket.discourse.group/t/cond-expand-in-racket/4000 "2025-11-14T18:48:49Z")
Hi, i have some code, not written by me, i want to port to Racket and it uses cond-expand (see SRFI 0) to adapt to each scheme implementation,for example Chicken or Guile had a feature guile that exists when guile compi… --- ## [Racket and DuckDB](https://racket.discourse.group/t/racket-and-duckdb/4003)
**Author:** [@jw\_gpc](https://racket.discourse.group/u/jw_gpc)\ **Replies:** 2\ **Last updated:** [November 13, 2025, 10:59am UTC](https://racket.discourse.group/t/racket-and-duckdb/4003 "2025-11-13T10:59:21Z")
Hello! I was wondering if anyone is using DuckDB with Racket. I know the db library works with SQLite, but I was interesting in trying out testing out DuckDB instead, and I haven't been able to find any references onli… [Previous page](https://racket.discourse.group/c/questions/6.md?page=1) [Next page](https://racket.discourse.group/c/questions/6.md?page=3)