# Latest **URL:** https://racket.discourse.group/latest.md?page=60 [Latest](https://racket.discourse.group/latest.md) · [Categories](https://racket.discourse.group/categories.md) · [Tags](https://racket.discourse.group/tags.md) **Page:** 61 --- ## [TIL: Inherited fields in structure subtypes are accessed with the accessor from the supertype](https://racket.discourse.group/t/til-inherited-fields-in-structure-subtypes-are-accessed-with-the-accessor-from-the-supertype/965)
**Author:** [@jamesgeddes](https://racket.discourse.group/u/jamesgeddes)\ **Replies:** 7\ **Last updated:** [May 5, 2022, 4:39pm UTC](https://racket.discourse.group/t/til-inherited-fields-in-structure-subtypes-are-accessed-with-the-accessor-from-the-supertype/965 "2022-05-05T16:39:47Z")
I thought you'd get at all fields in the subtype with accessors derived from the name of the subtype. No -- for supertype fields you use the supertype accessors. For example, if: A position is a pair of numbers: (stru… --- ## [Progress indicator for \`for\` loops: \`in-heartbeat\`](https://racket.discourse.group/t/progress-indicator-for-for-loops-in-heartbeat/960)
**Author:** [@soegaard](https://racket.discourse.group/u/soegaard)\ **Replies:** 3\ **Last updated:** [May 5, 2022, 1:51pm UTC](https://racket.discourse.group/t/progress-indicator-for-for-loops-in-heartbeat/960 "2022-05-05T13:51:43Z")
Waiting for the result of a large computation can be annoying. Is the loop stuck? The silly sequence below makes it easy to do something every nth time in a loop. Such as displaying a progress indicator. #lang racket… --- ## [What would it take to write an independent Racket interpreter?](https://racket.discourse.group/t/what-would-it-take-to-write-an-independent-racket-interpreter/951)
**Author:** [@MichaelBurge](https://racket.discourse.group/u/MichaelBurge)\ **Replies:** 9\ **Last updated:** [May 5, 2022, 1:28pm UTC](https://racket.discourse.group/t/what-would-it-take-to-write-an-independent-racket-interpreter/951 "2022-05-05T13:28:37Z")
Hello all, I was curious what it would take to "reimplement Racket". As a Scheme derivative, it has a small core language\[1\], but this includes only the language and no standard library. I found a nice folder\[2\] of tabl… --- ## [Should failures of "assert" use \`~e\` to control printout length?](https://racket.discourse.group/t/should-failures-of-assert-use-e-to-control-printout-length/958)
**Author:** [@jbclements](https://racket.discourse.group/u/jbclements)\ **Replies:** 3\ **Last updated:** [May 5, 2022, 5:35am UTC](https://racket.discourse.group/t/should-failures-of-assert-use-e-to-control-printout-length/958 "2022-05-05T05:35:01Z")
Here's a program: #lang typed/racket (assert (make-list 10000 "ouch") integer?) The assertion fails... but then it takes 10 seconds or so to print out the error message. Should this error message be abbreviate… --- ## [Raco pkg migrate](https://racket.discourse.group/t/raco-pkg-migrate/963)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 3\ **Last updated:** [May 3, 2022, 11:42pm UTC](https://racket.discourse.group/t/raco-pkg-migrate/963 "2022-05-03T23:42:54Z")
raco pkg migrate reinstalls all the packages you had in a previous installation Specifically, I just ran raco pkg migrate 8.4 after installing 8.5 (Copied from @benknoble on discord) --- ## [Racket v8.5 Released](https://racket.discourse.group/t/racket-v8-5-released/949)
**Author:** [@jbclements](https://racket.discourse.group/u/jbclements)\ **Replies:** 4\ **Last updated:** [May 3, 2022, 9:10pm UTC](https://racket.discourse.group/t/racket-v8-5-released/949 "2022-05-03T21:10:44Z")
Racket version 8.5 is now available from https://download.racket-lang.org. As of this release: Racket's new -y flag automatically keeps compiled files up to date, reducing subsequent load times. Error-message realms … --- ## [How are keywords different from symbols?](https://racket.discourse.group/t/how-are-keywords-different-from-symbols/959)
**Author:** [@MichaelBurge](https://racket.discourse.group/u/MichaelBurge)\ **Replies:** 4\ **Last updated:** [May 3, 2022, 5:44pm UTC](https://racket.discourse.group/t/how-are-keywords-different-from-symbols/959 "2022-05-03T17:44:17Z")
From a high-level understanding, I tend to think of keywords as being "a closed set of strings determined by your program's source code", while symbols are similar but the domain is at runtime. Neither usage is strict: … --- ## [TIL: numbers don't always print the same way](https://racket.discourse.group/t/til-numbers-dont-always-print-the-same-way/955)
**Author:** [@Laurent.O](https://racket.discourse.group/u/Laurent.O)\ **Replies:** 4\ **Last updated:** [May 3, 2022, 4:33pm UTC](https://racket.discourse.group/t/til-numbers-dont-always-print-the-same-way/955 "2022-05-03T16:33:39Z")
(merely trying out a today-i-learnt tag) Numbers may not print the same depending on the underlying formatter, even for base Racket. For example: \> (~r 1234567890123456789.123) "1234567890123456768" \> 12345678901234567… --- ## [Profiling example](https://racket.discourse.group/t/profiling-example/954)
**Author:** [@jbclements](https://racket.discourse.group/u/jbclements)\ **Replies:** 9\ **Last updated:** [May 3, 2022, 5:18am UTC](https://racket.discourse.group/t/profiling-example/954 "2022-05-03T05:18:01Z")
Do we have a wiki where we can put snippets of code? Or perhaps someone has time to format this as part of the docs? I wanted to run a profiler last night, and it looks like a piece of example code would be helpful. #la… --- ## [Scrolling \`racket/gui\` panels with the mouse](https://racket.discourse.group/t/scrolling-racket-gui-panels-with-the-mouse/957)
**Author:** [@benknoble](https://racket.discourse.group/u/benknoble)\ **Replies:** 3\ **Last updated:** [May 2, 2022, 10:46pm UTC](https://racket.discourse.group/t/scrolling-racket-gui-panels-with-the-mouse/957 "2022-05-02T22:46:57Z")
More context Tagging @bogdan so they can follow the thread. What would it take for racket/gui's panels to be scrollable via the mouse (i.e., without having to click and drag the scrollbar)? Bogdan has suggested racket/… --- ## [Learning racket/scheme - how do you get to the practicing stage?](https://racket.discourse.group/t/learning-racket-scheme-how-do-you-get-to-the-practicing-stage/901)
**Author:** [@maketo](https://racket.discourse.group/u/maketo)\ **Replies:** 64\ **Last updated:** [May 2, 2022, 9:36pm UTC](https://racket.discourse.group/t/learning-racket-scheme-how-do-you-get-to-the-practicing-stage/901 "2022-05-02T21:36:25Z")
This is kind of a self-admonishing rant, I do not expect any comments unless you really feel compelled. Been lurking here for a while, posted a few times. I have programmed for quite a few years now, started in quick bas… --- ## [Can I get the result of a match?](https://racket.discourse.group/t/can-i-get-the-result-of-a-match/943)
**Author:** [@robertpostill](https://racket.discourse.group/u/robertpostill)\ **Replies:** 2\ **Last updated:** [May 2, 2022, 10:25am UTC](https://racket.discourse.group/t/can-i-get-the-result-of-a-match/943 "2022-05-02T10:25:13Z")
I've been on a bit of a tear with match lately but I find myself re-running the match operation to take advantage of the match. For instance: define (find-email candidate) (define rule-name "Email Address") (define… --- ## [Tips / Tip of the day / Today I Learned category](https://racket.discourse.group/t/tips-tip-of-the-day-today-i-learned-category/937)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 6\ **Last updated:** [May 1, 2022, 10:27pm UTC](https://racket.discourse.group/t/tips-tip-of-the-day-today-i-learned-category/937 "2022-05-01T22:27:16Z")
@Laurent.O and @capfredf suggested a category for sharing tips / Today I Learned\* type content. If there are no objections I’ll create a new category on Sunday UK time. (If it becomes too noisy please remember you can … --- ## [A Functional Introduction to Computer Science (Part I)](https://racket.discourse.group/t/a-functional-introduction-to-computer-science-part-i/947)
**Author:** [@plragde](https://racket.discourse.group/u/plragde)\ **Replies:** 2\ **Last updated:** [May 1, 2022, 8:51pm UTC](https://racket.discourse.group/t/a-functional-introduction-to-computer-science-part-i/947 "2022-05-01T20:51:57Z")
I have a complete draft of the first part of my flânerie A Functional Introduction To Computer Science (Part I) up. Like my other flâneries, it's based on courses I developed at the University of Waterloo, but is self-co… --- ## [Giancarlo Rota's reminiscences](https://racket.discourse.group/t/giancarlo-rotas-reminiscences/668)
**Author:** [@jbclements](https://racket.discourse.group/u/jbclements)\ **Replies:** 0\ **Last updated:** [February 7, 2022, 11:05pm UTC](https://racket.discourse.group/t/giancarlo-rotas-reminiscences/668 "2022-02-07T23:05:07Z")
If you have any interest in mathematical logic, and you haven't read Giancarlo Rota's reminiscences of Princeton's math department in the 1950s, and more specifically his homage to Alonzo Church, I would urge you to do s… --- ## [\[Feature Request\] Improve error message for neglecting to (require (for-syntax racket/base))](https://racket.discourse.group/t/feature-request-improve-error-message-for-neglecting-to-require-for-syntax-racket-base/948)
**Author:** [@joskoot](https://racket.discourse.group/u/joskoot)\ **Replies:** 2\ **Last updated:** [May 1, 2022, 6:39pm UTC](https://racket.discourse.group/t/feature-request-improve-error-message-for-neglecting-to-require-for-syntax-racket-base/948 "2022-05-01T18:39:22Z")
See \[Feature Request\] Improve error message for neglecting to (require (for-syntax racket/base)) · Issue #3912 · racket/racket · GitHub I do not understand why (require (for-syntax racket/base)) is required. The follow… --- ## [About the Announcements category duplicate message](https://racket.discourse.group/t/about-the-announcements-category-duplicate-message/732)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 0\ **Last updated:** [February 25, 2022, 1:42am UTC](https://racket.discourse.group/t/about-the-announcements-category-duplicate-message/732 "2022-02-25T01:42:16Z")
The Announcements category is a low volume category for releases of the Racket distribution and other major announcements. Use your notification preferences to limit notifications to this category to the first post onl… --- ## [Keep white interactive background when saving pict to png file](https://racket.discourse.group/t/keep-white-interactive-background-when-saving-pict-to-png-file/940)
**Author:** [@albuck](https://racket.discourse.group/u/albuck)\ **Replies:** 3\ **Last updated:** [April 29, 2022, 11:23pm UTC](https://racket.discourse.group/t/keep-white-interactive-background-when-saving-pict-to-png-file/940 "2022-04-29T23:23:44Z")
I want to format some trees into png files. This code from StackOverflow makes a great diagram in the interactive window. When I follow the suggestion in the comment to save to a file, the png ends up with a solid blac… --- ## [@deftype and @defpolytype for Scribble](https://racket.discourse.group/t/deftype-and-defpolytype-for-scribble/935)
**Author:** [@scolobb](https://racket.discourse.group/u/scolobb)\ **Replies:** 2\ **Last updated:** [April 29, 2022, 10:05pm UTC](https://racket.discourse.group/t/deftype-and-defpolytype-for-scribble/935 "2022-04-29T22:05:49Z")
Hello, While writing Scribble docs for my Typed Racket code, I ended up with the following macros: @(define-syntax-rule (defpolytype . args) (defform #:kind "polymorphic type" . args)) @(define-syntax-rule (deftype … --- ## [Package seems not to be updated](https://racket.discourse.group/t/package-seems-not-to-be-updated/874)
**Author:** [@simonls](https://racket.discourse.group/u/simonls)\ **Replies:** 10\ **Last updated:** [April 29, 2022, 7:18pm UTC](https://racket.discourse.group/t/package-seems-not-to-be-updated/874 "2022-04-29T19:18:54Z")
Since: the package server seems to be stuck, not updating the package. The package name stayed the same, however it points to a git repository that was renamed to make the case consistent with the package name. Can so… --- ## [Qi++: Qi but with Real Macros](https://racket.discourse.group/t/qi-qi-but-with-real-macros/871)
**Author:** [@countvajhula](https://racket.discourse.group/u/countvajhula)\ **Replies:** 13\ **Last updated:** [April 28, 2022, 11:54pm UTC](https://racket.discourse.group/t/qi-qi-but-with-real-macros/871 "2022-04-28T23:54:34Z")
Just kidding, it isn't really called Qi++ :stuck\_out\_tongue\_closed\_eyes: . It's the same old Qi, but it now does have real macros! What does that mean? Well, some time ago this paper about making DSLs "macro extensible… --- ## [Preventing unnoticed thread death](https://racket.discourse.group/t/preventing-unnoticed-thread-death/931)
**Author:** [@dstorrs](https://racket.discourse.group/u/dstorrs)\ **Replies:** 5\ **Last updated:** [April 28, 2022, 2:36pm UTC](https://racket.discourse.group/t/preventing-unnoticed-thread-death/931 "2022-04-28T14:36:51Z")
I'm expanding the majordomo2 task management module to accept a max-workers parameter such that number of running tasks can be constrained with newly-added tasks being queued until there are workers available. My initia… --- ## [Where can I find examples of engines?](https://racket.discourse.group/t/where-can-i-find-examples-of-engines/915)
**Author:** [@dstorrs](https://racket.discourse.group/u/dstorrs)\ **Replies:** 9\ **Last updated:** [April 28, 2022, 1:22pm UTC](https://racket.discourse.group/t/where-can-i-find-examples-of-engines/915 "2022-04-28T13:22:03Z")
I was reading about Racket's 11.6 Engines concept and thought it was pretty interesting. Are there any examples of them in use? I looked in the Guide but didn't see a mention of them, and my Google-fu is turning up not… --- ## [\`raco pkg migrate\` for \`--link\` and \`--no-setup\` packages](https://racket.discourse.group/t/raco-pkg-migrate-for-link-and-no-setup-packages/926)
**Author:** [@greghendershott](https://racket.discourse.group/u/greghendershott)\ **Replies:** 3\ **Last updated:** [April 26, 2022, 4:48pm UTC](https://racket.discourse.group/t/raco-pkg-migrate-for-link-and-no-setup-packages/926 "2022-04-26T16:48:34Z")
How does raco pkg migrate handle linked packages (those originally installed with --link from a directory package source)? Does it: Copy (ala --copy), such that the original's compiled remains in the original link s… --- ## [How to run interactively from terminal?](https://racket.discourse.group/t/how-to-run-interactively-from-terminal/918)
**Author:** [@jkleiser](https://racket.discourse.group/u/jkleiser)\ **Replies:** 7\ **Last updated:** [April 26, 2022, 8:49am UTC](https://racket.discourse.group/t/how-to-run-interactively-from-terminal/918 "2022-04-26T08:49:26Z")
In my code I have a function that I would like to call while in the REPL in my macOS Terminal. I start my code like this: racket -i my-code.rkt However, if I try to execute my function, doing (my-fun), I get this error … --- ## [Is it possible to use "s-exp" reader to parse expressions without parens wrapped?](https://racket.discourse.group/t/is-it-possible-to-use-s-exp-reader-to-parse-expressions-without-parens-wrapped/924)
**Author:** [@doublex](https://racket.discourse.group/u/doublex)\ **Replies:** 4\ **Last updated:** [April 25, 2022, 8:28pm UTC](https://racket.discourse.group/t/is-it-possible-to-use-s-exp-reader-to-parse-expressions-without-parens-wrapped/924 "2022-04-25T20:28:19Z")
Hi, I'm trying to implement a typed language using Racket's LOP. since my calculus requires full annotation, it will be ugly to write code like (λ (x : t1) e t2) It becomes worser when lambda expression are nested lik… --- ## [Please can I use sgl to draw to a bitmap](https://racket.discourse.group/t/please-can-i-use-sgl-to-draw-to-a-bitmap/923)
**Author:** [@hendrikboom3](https://racket.discourse.group/u/hendrikboom3)\ **Replies:** 2\ **Last updated:** [April 25, 2022, 4:35pm UTC](https://racket.discourse.group/t/please-can-i-use-sgl-to-draw-to-a-bitmap/923 "2022-04-25T16:35:08Z")
I am currently using sgl to draw to a window, and using the screenshot progrm to convert the picture to a .png file. Unfortunately, this seems to limut the png to screen size, and I need more pixels than that for my app… --- ## [Shared data structures between parallel workers in racket?](https://racket.discourse.group/t/shared-data-structures-between-parallel-workers-in-racket/909)
**Author:** [@yak](https://racket.discourse.group/u/yak)\ **Replies:** 11\ **Last updated:** [April 24, 2022, 1:04am UTC](https://racket.discourse.group/t/shared-data-structures-between-parallel-workers-in-racket/909 "2022-04-24T01:04:49Z")
We are working on parallelizing a long computation in racket so that it can take advantage of multiple cores while sharing data structures, and are hoping for some advice from the community. The computation consists of … --- ## [Where to start/what to do/intro projects](https://racket.discourse.group/t/where-to-start-what-to-do-intro-projects/920)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 0\ **Last updated:** [April 23, 2022, 1:14pm UTC](https://racket.discourse.group/t/where-to-start-what-to-do-intro-projects/920 "2022-04-23T13:14:24Z")
A few days ago a new Racket user asked: Say I've read the guides and a couple of the books, how can I find things to code? I feel stuck as I've learnt a bit of Racket, but don't have a clue what to create unfortunately… --- ## [Reusable tests, test-cases, and test-suites](https://racket.discourse.group/t/reusable-tests-test-cases-and-test-suites/884)
**Author:** [@dominik.pantucek](https://racket.discourse.group/u/dominik.pantucek)\ **Replies:** 4\ **Last updated:** [April 23, 2022, 11:00am UTC](https://racket.discourse.group/t/reusable-tests-test-cases-and-test-suites/884 "2022-04-23T11:00:35Z")
Hello fellow Racketeers, while preparing some lecture notes I noticed that sometimes it is useful to have a multiple implementations of single algorithm prepared. As I am playing with this idea, I started to write ident… [Previous page](https://racket.discourse.group/latest.md?page=59) [Next page](https://racket.discourse.group/latest.md?page=61)