# Latest **URL:** https://racket.discourse.group/latest.md?page=67 [Latest](https://racket.discourse.group/latest.md) · [Categories](https://racket.discourse.group/categories.md) · [Tags](https://racket.discourse.group/tags.md) **Page:** 68 --- ## [ELS 2022, Porto - European Lisp Symposium](https://racket.discourse.group/t/els-2022-porto-european-lisp-symposium/544)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 0\ **Last updated:** [January 10, 2022, 3:07pm UTC](https://racket.discourse.group/t/els-2022-porto-european-lisp-symposium/544 "2022-01-10T15:07:15Z")
Apparently there are only a few days left to send papers for the ELS2022! --- ## [Racket Meetup: Saturday January 8, 2022](https://racket.discourse.group/t/racket-meetup-saturday-january-8-2022/390)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 8\ **Last updated:** [January 9, 2022, 12:30pm UTC](https://racket.discourse.group/t/racket-meetup-saturday-january-8-2022/390 "2022-01-09T12:30:52Z")
Racket Meetup: Saturday January 8, 2022 2022-01-08T18:00:00Z (UTC) Where: https://gather.town/app/wH1EDG3McffLjrs0/racket-users When: First Saturday EVERY Month UTC: 18:00 30 minutes but can overrun --- ## [Writing a macro that behaves differently depending on context](https://racket.discourse.group/t/writing-a-macro-that-behaves-differently-depending-on-context/536)
**Author:** [@dimaugh](https://racket.discourse.group/u/dimaugh)\ **Replies:** 2\ **Last updated:** [January 8, 2022, 10:51am UTC](https://racket.discourse.group/t/writing-a-macro-that-behaves-differently-depending-on-context/536 "2022-01-08T10:51:57Z")
I'm trying to define a macro 'def' which behaves differently depending on where it appears. If it appears in the top-level, it expands to a normal 'define' and adds the definition to a hash. If it appears in a local cont… --- ## [Rhombus meeting today (Jan 6, 2022)](https://racket.discourse.group/t/rhombus-meeting-today-jan-6-2022/531)
**Author:** [@notjack](https://racket.discourse.group/u/notjack)\ **Replies:** 0\ **Last updated:** [January 6, 2022, 9:02pm UTC](https://racket.discourse.group/t/rhombus-meeting-today-jan-6-2022/531 "2022-01-06T21:02:27Z")
Rhombus meeting today! We’re talking about the Wraith syntax proposal. Agenda: Rhombus bi-weekly virtual meeting · Discussion #180 · racket/rhombus-prototype · GitHub Zoom link: Launch Meeting - Zoom --- ## [Implementing debug vs production versions?](https://racket.discourse.group/t/implementing-debug-vs-production-versions/527)
**Author:** [@dstorrs](https://racket.discourse.group/u/dstorrs)\ **Replies:** 4\ **Last updated:** [January 6, 2022, 7:33pm UTC](https://racket.discourse.group/t/implementing-debug-vs-production-versions/527 "2022-01-06T19:33:00Z")
Suppose I have this code: (define (foo) (if (getenv "DEBUG") plausible-test-value (expensive-function-call-that-determines-the-actual-value))) Perhaps the production version requires a network connectio… --- ## [Best way to create a web-based app to graph temperature data](https://racket.discourse.group/t/best-way-to-create-a-web-based-app-to-graph-temperature-data/522)
**Author:** [@LaughingWater](https://racket.discourse.group/u/LaughingWater)\ **Replies:** 5\ **Last updated:** [January 5, 2022, 8:31pm UTC](https://racket.discourse.group/t/best-way-to-create-a-web-based-app-to-graph-temperature-data/522 "2022-01-05T20:31:20Z")
Consider me a newbie. I'm re-writing my LispWorks refrigeration-monitoring app in Racket with hopes of making it web-based. It needs to draw a graph of temperatures over time, preferably scrollable so we can see anomalie… --- ## [TIL: Enforcing contracts with \`contract-out\` from within an embedded test module](https://racket.discourse.group/t/til-enforcing-contracts-with-contract-out-from-within-an-embedded-test-module/525)
**Author:** [@sschwarzer](https://racket.discourse.group/u/sschwarzer)\ **Replies:** 1\ **Last updated:** [January 4, 2022, 10:40pm UTC](https://racket.discourse.group/t/til-enforcing-contracts-with-contract-out-from-within-an-embedded-test-module/525 "2022-01-04T22:40:28Z")
TL;DR :wink: It's possible to enforce and test contracts defined at the module boundary within a test module in the same file. Do this by require'ing (submod "..") in the test module: (module+ test (require ... … --- ## [Trying to learn macros, have question on code snippet](https://racket.discourse.group/t/trying-to-learn-macros-have-question-on-code-snippet/523)
**Author:** [@maketo](https://racket.discourse.group/u/maketo)\ **Replies:** 4\ **Last updated:** [January 4, 2022, 7:45pm UTC](https://racket.discourse.group/t/trying-to-learn-macros-have-question-on-code-snippet/523 "2022-01-04T19:45:44Z")
Hello. I am new to Scheme/Racket (not to programming) and am trying to learn Racket through BeautifulRacket. After a few chapters I got interested in learning more about Racket's macro capabilities (before going back to … --- ## [\`#:methods gen:custom-write\` replacement in typed/racket?](https://racket.discourse.group/t/methods-gen-custom-write-replacement-in-typed-racket/521)
**Author:** [@dannypsnl](https://racket.discourse.group/u/dannypsnl)\ **Replies:** 1\ **Last updated:** [January 4, 2022, 6:58pm UTC](https://racket.discourse.group/t/methods-gen-custom-write-replacement-in-typed-racket/521 "2022-01-04T18:58:02Z")
Probably silly, but I don't want to affect any existing code that relies on gen:custom-write (struct vec3 (x y z) #:methods gen:custom-write \[(define (write-proc v port mode) (fprintf port "~a ~a ~a" (vec3-x v)… --- ## [Typed racket production quality?](https://racket.discourse.group/t/typed-racket-production-quality/524)
**Author:** [@maketo](https://racket.discourse.group/u/maketo)\ **Replies:** 2\ **Last updated:** [January 4, 2022, 5:02pm UTC](https://racket.discourse.group/t/typed-racket-production-quality/524 "2022-01-04T17:02:54Z")
Hello. Since I am new to Racket (coming from Pascal-\>asm-\>C-\>python-\>Scala) - is Typed Racket "production" quality? In other words, types etc. are part of Scala, enforced properly etc. Can I count on typed racket having … --- ## [Test environment on package server](https://racket.discourse.group/t/test-environment-on-package-server/512)
**Author:** [@sschwarzer](https://racket.discourse.group/u/sschwarzer)\ **Replies:** 4\ **Last updated:** [January 4, 2022, 12:58pm UTC](https://racket.discourse.group/t/test-environment-on-package-server/512 "2022-01-04T12:58:31Z")
For one of my packages, there are failing tests in the package server environment, although the tests succeed on my machine. From the package server's error log it looks like (find-executable-path "raco") doesn't find r… --- ## [Accessing discourse list via nntp](https://racket.discourse.group/t/accessing-discourse-list-via-nntp/515)
**Author:** [@mark](https://racket.discourse.group/u/mark)\ **Replies:** 5\ **Last updated:** [January 3, 2022, 6:01pm UTC](https://racket.discourse.group/t/accessing-discourse-list-via-nntp/515 "2022-01-03T18:01:13Z")
I read the racket mailing lists via nntp via gmane.io Could the discourse lists be setup to at least allow reading via nntp (I think writing ends up being like writing to the maiuling list - ie the poster has to registe… --- ## [Automatic Differentiation in Racket](https://racket.discourse.group/t/automatic-differentiation-in-racket/519)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 0\ **Last updated:** [January 3, 2022, 3:18pm UTC](https://racket.discourse.group/t/automatic-differentiation-in-racket/519 "2022-01-03T15:18:19Z")
Note: I didn’t make either of these but I thought it was worth sharing neither are on the package catalog rackpropagator Exploring Automatic Differentiation in Racket https://www.lambdadays.org/lambdadays2020/oliver-… --- ## [Difference between \`fail\` and \`fail-check\`?](https://racket.discourse.group/t/difference-between-fail-and-fail-check/506)
**Author:** [@sschwarzer](https://racket.discourse.group/u/sschwarzer)\ **Replies:** 5\ **Last updated:** [January 2, 2022, 11:20pm UTC](https://racket.discourse.group/t/difference-between-fail-and-fail-check/506 "2022-01-02T23:20:51Z")
Happy New Year everyone! :slight\_smile: The rackunit documentation describes two functions: fail fail-check From the descriptions both functions seem very similar, - so similar that I'm not sure when I should use wh… --- ## [Get creation date from a file function missing?](https://racket.discourse.group/t/get-creation-date-from-a-file-function-missing/487)
**Author:** [@kurinoku](https://racket.discourse.group/u/kurinoku)\ **Replies:** 3\ **Last updated:** [December 29, 2021, 10:50pm UTC](https://racket.discourse.group/t/get-creation-date-from-a-file-function-missing/487 "2021-12-29T22:50:37Z")
The procedure file-or-directory-modify-seconds exists, yet I can't seem to find a similar function for the creation date. --- ## [Threads waiting for a worker thread to make progress](https://racket.discourse.group/t/threads-waiting-for-a-worker-thread-to-make-progress/507)
**Author:** [@greghendershott](https://racket.discourse.group/u/greghendershott)\ **Replies:** 2\ **Last updated:** [January 1, 2022, 10:02pm UTC](https://racket.discourse.group/t/threads-waiting-for-a-worker-thread-to-make-progress/507 "2022-01-01T22:02:37Z")
If anyone would like to help review a little thread synchronization, I have an example. The motivation: A worker thread updates (set!s) a couple increasing integer variables. Some other threads need to wait until … --- ## [Raco-exe-multitarget](https://racket.discourse.group/t/raco-exe-multitarget/509)
**Author:** [@sschwarzer](https://racket.discourse.group/u/sschwarzer)\ **Replies:** 0\ **Last updated:** [January 1, 2022, 8:28pm UTC](https://racket.discourse.group/t/raco-exe-multitarget/509 "2022-01-01T20:28:10Z")
Following up on a recent topic, I created a package raco-exe-multitarget. The package relies on raco-cross to implement a raco command exe-multitarget to create standalone binaries for multiple platforms in one go. Here… --- ## [Parallelizing the Racket Web Server](https://racket.discourse.group/t/parallelizing-the-racket-web-server/502)
**Author:** [@bogdan](https://racket.discourse.group/u/bogdan)\ **Replies:** 3\ **Last updated:** [January 1, 2022, 3:35pm UTC](https://racket.discourse.group/t/parallelizing-the-racket-web-server/502 "2022-01-01T15:35:14Z")
I wrote a blog post about using places & units to parallelize Racket web apps. Feedback welcome! --- ## [Where does raco stores collections on macOS?](https://racket.discourse.group/t/where-does-raco-stores-collections-on-macos/495)
**Author:** [@dannypsnl](https://racket.discourse.group/u/dannypsnl)\ **Replies:** 8\ **Last updated:** [December 31, 2021, 8:43pm UTC](https://racket.discourse.group/t/where-does-raco-stores-collections-on-macos/495 "2021-12-31T20:43:22Z")
I just found when I type raco install --auto xxx, it says missing xxx/yyy in /home/Library/Racket/8.3/collects /Applications/Racket v8.3/collects/ but end up I found xxx/yyy is existed in /home/Library/Racket/8.3/pkgs… --- ## [Rackcheck question: How to name a property?](https://racket.discourse.group/t/rackcheck-question-how-to-name-a-property/484)
**Author:** [@danprager](https://racket.discourse.group/u/danprager)\ **Replies:** 6\ **Last updated:** [December 31, 2021, 7:41am UTC](https://racket.discourse.group/t/rackcheck-question-how-to-name-a-property/484 "2021-12-31T07:41:06Z")
I've just started using @bogdan's nice property-testing package rackcheck (includes shrinking!), and I can't figure out the syntax for adding a name to a property. I'd like to give a name to my property ahead of adding … --- ## [A language and REPL for SRFI 105 "curly infix"](https://racket.discourse.group/t/a-language-and-repl-for-srfi-105-curly-infix/501)
**Author:** [@damien\_mattei](https://racket.discourse.group/u/damien_mattei)\ **Replies:** 0\ **Last updated:** [December 30, 2021, 10:57pm UTC](https://racket.discourse.group/t/a-language-and-repl-for-srfi-105-curly-infix/501 "2021-12-30T22:57:52Z")
Hi, i adapted a #lang and REPL for SRFI 105: https://github.com/damien-mattei/library-FunctProg/blob/master/racket/SRFI-105.rkt a simple example can be found here: https://github.com/damien-mattei/library-FunctProg/b… --- ## [Racket Error:arity mismatch;](https://racket.discourse.group/t/racket-error-arity-mismatch/498)
**Author:** [@osman44](https://racket.discourse.group/u/osman44)\ **Replies:** 5\ **Last updated:** [December 30, 2021, 10:49pm UTC](https://racket.discourse.group/t/racket-error-arity-mismatch/498 "2021-12-30T22:49:11Z")
I am trying to create a function in which takes two aruguments in my case i want the function to return true only when both arguements are true and false otherwise.So in my function i want it to ask the user to "whats th… --- ## [Todo-txt: todo.txt parser and report tool](https://racket.discourse.group/t/todo-txt-todo-txt-parser-and-report-tool/499)
**Author:** [@sschwarzer](https://racket.discourse.group/u/sschwarzer)\ **Replies:** 0\ **Last updated:** [December 30, 2021, 6:34pm UTC](https://racket.discourse.group/t/todo-txt-todo-txt-parser-and-report-tool/499 "2021-12-30T18:34:38Z")
I've written a library and command line tool to process files following the todo.txt format. todo.txt format overview Each line in a todo.txt file is of the form: x (A) 2021-12-30 2021-12-28 Task with a project +my-pro… --- ## [Error in syntax-parse](https://racket.discourse.group/t/error-in-syntax-parse/494)
**Author:** [@damien\_mattei](https://racket.discourse.group/u/damien_mattei)\ **Replies:** 4\ **Last updated:** [December 30, 2021, 3:51pm UTC](https://racket.discourse.group/t/error-in-syntax-parse/494 "2021-12-30T15:51:59Z")
hello, i have this error in this code: #lang racket (require syntax/parse) (require syntax/strip-context) (define (emit-interaction stx) (syntax-parse stx #:context '|error while parsing interaction| \[(\_ expr-o… --- ## [Storing code for later evaluation at runtime](https://racket.discourse.group/t/storing-code-for-later-evaluation-at-runtime/485)
**Author:** [@rscho](https://racket.discourse.group/u/rscho)\ **Replies:** 2\ **Last updated:** [December 30, 2021, 5:51am UTC](https://racket.discourse.group/t/storing-code-for-later-evaluation-at-runtime/485 "2021-12-30T05:51:40Z")
Hi, I'm constructing a struct/dc contract through a macro. The real contract specs would only be known at struct instantiation time late into execution, and I need to store the original contract and modify it according… --- ## [Cant write function to return opposite true/false](https://racket.discourse.group/t/cant-write-function-to-return-opposite-true-false/489)
**Author:** [@osman44](https://racket.discourse.group/u/osman44)\ **Replies:** 2\ **Last updated:** [December 29, 2021, 6:40pm UTC](https://racket.discourse.group/t/cant-write-function-to-return-opposite-true-false/489 "2021-12-29T18:40:14Z")
I have been trying to write a function in racket which takes one argument returns its opposite so in my example i have been trying to set b to equal 4 and if any other value is entered it should return true but in my cas… --- ## [\[Feature Request\] Tag Contract and Tag Type](https://racket.discourse.group/t/feature-request-tag-contract-and-tag-type/427)
**Author:** [@NoahStoryM](https://racket.discourse.group/u/NoahStoryM)\ **Replies:** 2\ **Last updated:** [December 28, 2021, 11:46am UTC](https://racket.discourse.group/t/feature-request-tag-contract-and-tag-type/427 "2021-12-28T11:46:11Z")
Hello everyone, I want to share some thoughts I encountered when using Typed Racket. I don't have too deep theoretical foundation and knowledge accumulation, so it may be a little naive. :slight\_smile: Recently, I want … --- ## [SRFI 105 as a Racket language, need a few help](https://racket.discourse.group/t/srfi-105-as-a-racket-language-need-a-few-help/482)
**Author:** [@damien\_mattei](https://racket.discourse.group/u/damien_mattei)\ **Replies:** 4\ **Last updated:** [December 28, 2021, 7:27pm UTC](https://racket.discourse.group/t/srfi-105-as-a-racket-language-need-a-few-help/482 "2021-12-28T19:27:49Z")
hello, i'm porting SRFI 105 "Curly infix" to Racket. I wrote a "reader" that works and the SRFI 105 is packaged with a REPL that works already with little change (only one line modified as far as ia can remember) but i… --- ## [Qi is now "macro extensible"](https://racket.discourse.group/t/qi-is-now-macro-extensible/471)
**Author:** [@countvajhula](https://racket.discourse.group/u/countvajhula)\ **Replies:** 6\ **Last updated:** [December 27, 2021, 10:39pm UTC](https://racket.discourse.group/t/qi-is-now-macro-extensible/471 "2021-12-27T22:39:29Z")
Some time ago I noticed the paper by Ballantyne et. al. re: making your DSL "macro extensible," with the idea to implement it for Qi. The paper was way over my head so I've had it on the backburner to eventually spend mo… --- ## [Racket set performance](https://racket.discourse.group/t/racket-set-performance/479)
**Author:** [@badkins](https://racket.discourse.group/u/badkins)\ **Replies:** 11\ **Last updated:** [December 27, 2021, 8:32pm UTC](https://racket.discourse.group/t/racket-set-performance/479 "2021-12-27T20:32:02Z")
I ported a Python version of Advent of Code Day 25 to this Racket version , and I was surprised by what appears to be the relatively poor performance of Racket's set implementation. The Python version runs in about 1.5 … [Previous page](https://racket.discourse.group/latest.md?page=66) [Next page](https://racket.discourse.group/latest.md?page=68)