# Questions & Answers **URL:** https://racket.discourse.group/c/questions/6.md?page=19 [Latest](https://racket.discourse.group/latest.md) · [Categories](https://racket.discourse.group/categories.md) · [Tags](https://racket.discourse.group/tags.md) **Page:** 20 --- ## [How to set focus to the only button?](https://racket.discourse.group/t/how-to-set-focus-to-the-only-button/2270)
**Author:** [@Vadim\_Y](https://racket.discourse.group/u/Vadim_Y)\ **Replies:** 5\ **Last updated:** [September 2, 2023, 2:22pm UTC](https://racket.discourse.group/t/how-to-set-focus-to-the-only-button/2270 "2023-09-02T14:22:07Z")
Hello! How to set focus to the only button in the application when it starts? --- ## [What is \`raco demod\` for?](https://racket.discourse.group/t/what-is-raco-demod-for/2272)
**Author:** [@spdegabrielle](https://racket.discourse.group/u/spdegabrielle)\ **Replies:** 1\ **Last updated:** [September 1, 2023, 5:07pm UTC](https://racket.discourse.group/t/what-is-raco-demod-for/2272 "2023-09-01T17:07:32Z")
What is raco demod for? and why would you want to demodularize your programs? I'm guessing it makes the resulting code smaller or faster?, but I also want to know what the trade-off is? What do you lose when you demodul… --- ## [Calling into a Chez Scheme library from Racket -- imported symbol rewritten in vm-eval?](https://racket.discourse.group/t/calling-into-a-chez-scheme-library-from-racket-imported-symbol-rewritten-in-vm-eval/2257)
**Author:** [@awwx](https://racket.discourse.group/u/awwx)\ **Replies:** 9\ **Last updated:** [September 1, 2023, 2:15am UTC](https://racket.discourse.group/t/calling-into-a-chez-scheme-library-from-racket-imported-symbol-rewritten-in-vm-eval/2257 "2023-09-01T02:15:31Z")
I have a Chez Scheme library "foo.ss" that I'd like to call from Racket: (library (foo) (export bar) (import (rnrs)) (define (bar) "hello")) From Chez Scheme: $ chezscheme Chez Scheme Version 9.5.4 Copyright… --- ## [Windows 10 Aspell Not Responding from DrRacket](https://racket.discourse.group/t/windows-10-aspell-not-responding-from-drracket/2255)
**Author:** [@bakgatviooldoos](https://racket.discourse.group/u/bakgatviooldoos)\ **Replies:** 0\ **Last updated:** [August 28, 2023, 10:50am UTC](https://racket.discourse.group/t/windows-10-aspell-not-responding-from-drracket/2255 "2023-08-28T10:50:10Z")
Hi, Racket Discourse. I am trying to get the spell checker to work in DrRacket on Windows 10 but I keep receiving the following error: The spell program (C:\\msys64\\mingw64\\bin\\aspell.exe) did not respond after 0.1 sec… --- ## [How to run REPL in command-line Racket with another language?](https://racket.discourse.group/t/how-to-run-repl-in-command-line-racket-with-another-language/1848)
**Author:** [@Kalimehtar](https://racket.discourse.group/u/Kalimehtar)\ **Replies:** 7\ **Last updated:** [August 27, 2023, 3:40am UTC](https://racket.discourse.group/t/how-to-run-repl-in-command-line-racket-with-another-language/1848 "2023-08-27T03:40:30Z")
In DrRacket I can simply set #lang basic-demo-3, then in REPL say \> let x = 5 \> print x 5 In command line I tried racket -I basic-demo-3 but it doesn't work. $ racket -I basic-demo-3 Welcome to Racket v8.7 \[cs\]. \> l… --- ## [Open an rkt file in windows](https://racket.discourse.group/t/open-an-rkt-file-in-windows/2250)
**Author:** [@joskoot](https://racket.discourse.group/u/joskoot)\ **Replies:** 5\ **Last updated:** [August 26, 2023, 8:36am UTC](https://racket.discourse.group/t/open-an-rkt-file-in-windows/2250 "2023-08-26T08:36:52Z")
Windows 10, Racket version 8.10.0.1--2023-07-17(1aa7d3d809/a) \[cs\]. When I open a .rkt or .scrbl file by double clicking it and DrRacket is not yet running, DrRacket starts, but it fails with: No problem starting Dr… --- ## [Cannot (require ...) in module inside macro](https://racket.discourse.group/t/cannot-require-in-module-inside-macro/2241)
**Author:** [@axmx](https://racket.discourse.group/u/axmx)\ **Replies:** 10\ **Last updated:** [August 25, 2023, 1:05am UTC](https://racket.discourse.group/t/cannot-require-in-module-inside-macro/2241 "2023-08-25T01:05:02Z")
When using (require rackunit) in a macro, the identifiers are not properly imported, and I get this error: test2.rkt:11:1: check-equal: unbound identifier in: check-equal #(169 11) Minimal example: #lang racket (… --- ## [Smtp-send-message and tls version](https://racket.discourse.group/t/smtp-send-message-and-tls-version/2238)
**Author:** [@markshead](https://racket.discourse.group/u/markshead)\ **Replies:** 1\ **Last updated:** [August 22, 2023, 11:54pm UTC](https://racket.discourse.group/t/smtp-send-message-and-tls-version/2238 "2023-08-22T23:54:21Z")
The code below works for sending emails, but I'm getting messages from AWS SES saying that those messages are being sent with tls 1.0 or 1.1 which is deprecated and will be unavailable soon. If I understand it correctly… --- ## [Why does write-bytes-avail-evt not return an error?](https://racket.discourse.group/t/why-does-write-bytes-avail-evt-not-return-an-error/2230)
**Author:** [@janus](https://racket.discourse.group/u/janus)\ **Replies:** 3\ **Last updated:** [August 22, 2023, 4:36pm UTC](https://racket.discourse.group/t/why-does-write-bytes-avail-evt-not-return-an-error/2230 "2023-08-22T16:36:50Z")
I am trying to find how how I can handle all the errors that can happen related to a TCP connection. So I have written this server: #lang racket/base (require racket/tcp) (define listener (tcp-listen 8000)) (define o (… --- ## [Newbie Trouble using Scribble Links](https://racket.discourse.group/t/newbie-trouble-using-scribble-links/2237)
**Author:** [@bakgatviooldoos](https://racket.discourse.group/u/bakgatviooldoos)\ **Replies:** 8\ **Last updated:** [August 22, 2023, 10:20am UTC](https://racket.discourse.group/t/newbie-trouble-using-scribble-links/2237 "2023-08-22T10:20:29Z")
Hi, Racket Discourse. I am busy preparing some documentation for a presentation that I have to do this afternoon, but I am banging my head against a wall trying to use Scribble section references and the like. All I wa… --- ## [Do not understand stateful vs stateless servlets](https://racket.discourse.group/t/do-not-understand-stateful-vs-stateless-servlets/2220)
**Author:** [@hendrikboom3](https://racket.discourse.group/u/hendrikboom3)\ **Replies:** 1\ **Last updated:** [August 19, 2023, 8:02pm UTC](https://racket.discourse.group/t/do-not-understand-stateful-vs-stateless-servlets/2220 "2023-08-19T20:02:16Z")
I don't understand what stateful and stateless servlets are about. As far as I can tell, the documentation at Web Applications in Racket describes a lot of functions that can be used to interact with the web server, … --- ## [Traits documentation bug](https://racket.discourse.group/t/traits-documentation-bug/2199)
**Author:** [@matteo-daddio](https://racket.discourse.group/u/matteo-daddio)\ **Replies:** 4\ **Last updated:** [August 19, 2023, 6:19pm UTC](https://racket.discourse.group/t/traits-documentation-bug/2199 "2023-08-19T18:19:50Z")
Hello, I think I’ve spotted a bug in the racket guide, here: 13 Classes and Objects It’s about traits. In the marked line get-color and get-price are reversed. Is this a bug? Matteo --- ## [What locale is for string-upcase?](https://racket.discourse.group/t/what-locale-is-for-string-upcase/2203)
**Author:** [@Kalimehtar](https://racket.discourse.group/u/Kalimehtar)\ **Replies:** 8\ **Last updated:** [August 18, 2023, 7:34pm UTC](https://racket.discourse.group/t/what-locale-is-for-string-upcase/2203 "2023-08-18T19:34:38Z")
(parameterize (\[current-locale #f\]) (string-locale-upcase "Straße")) ; =\> "STRAßE" (string-upcase "Straße") ; =\> "STRASSE" The documentation states, that string-upcase "uses Unicode’s locale-independent conversion ru… --- ## [Example of a lang lexer that returns a \`dont-stop\` struct?](https://racket.discourse.group/t/example-of-a-lang-lexer-that-returns-a-dont-stop-struct/438)
**Author:** [@greghendershott](https://racket.discourse.group/u/greghendershott)\ **Replies:** 4\ **Last updated:** [August 18, 2023, 12:39pm UTC](https://racket.discourse.group/t/example-of-a-lang-lexer-that-returns-a-dont-stop-struct/438 "2023-08-18T12:39:43Z")
A lang's module lexer can return a dont-stop struct. I would like to test my handling of that. But so far (with e.g. langs racket, rhombus, and scribble/manual) I'm never seeing a dont-stop. What's an example of such … --- ## [How to create an identifier from a procedure](https://racket.discourse.group/t/how-to-create-an-identifier-from-a-procedure/2219)
**Author:** [@damien\_mattei](https://racket.discourse.group/u/damien_mattei)\ **Replies:** 14\ **Last updated:** [August 18, 2023, 6:57am UTC](https://racket.discourse.group/t/how-to-create-an-identifier-from-a-procedure/2219 "2023-08-18T06:57:52Z")
(define-syntax bar (syntax-rules () ((\_ proc) (require (rename-in racket/base (proc identifier)))))) how can i create identifier to be like base:proc example (bar +) identifier would be bas… --- ## [Signature types](https://racket.discourse.group/t/signature-types/2226)
**Author:** [@ahsatan](https://racket.discourse.group/u/ahsatan)\ **Replies:** 2\ **Last updated:** [August 18, 2023, 12:20am UTC](https://racket.discourse.group/t/signature-types/2226 "2023-08-18T00:20:05Z")
Hello! I'm playing around with the newish Signatures feature on some very simple code and am not sure if this isn't expected to work yet (I read it's experimental in the previous patch) or I'm doing something wrong: (… --- ## [DrRacket trait form unknown](https://racket.discourse.group/t/drracket-trait-form-unknown/2218)
**Author:** [@matteo-daddio](https://racket.discourse.group/u/matteo-daddio)\ **Replies:** 2\ **Last updated:** [August 14, 2023, 3:00pm UTC](https://racket.discourse.group/t/drracket-trait-form-unknown/2218 "2023-08-14T15:00:14Z")
Hello, I’m trying to work with traits, but DrRacket gives me this error: What can it be? Matteo --- ## [Color lexer backup distances and \`dont-stop\`](https://racket.discourse.group/t/color-lexer-backup-distances-and-dont-stop/2170)
**Author:** [@LiberalArtist](https://racket.discourse.group/u/LiberalArtist)\ **Replies:** 8\ **Last updated:** [August 12, 2023, 5:46am UTC](https://racket.discourse.group/t/color-lexer-backup-distances-and-dont-stop/2170 "2023-08-12T05:46:47Z")
I'm trying to implement a color lexer for the syntax of .gitignore files. For reasons I'll explain, I think I need non-zero backup distances and dont-stop, which have always confused me, and I want to check my understand… --- ## [The Little Typer: implicattion that values are not neutral?](https://racket.discourse.group/t/the-little-typer-implicattion-that-values-are-not-neutral/1737)
**Author:** [@rebcabin](https://racket.discourse.group/u/rebcabin)\ **Replies:** 4\ **Last updated:** [August 11, 2023, 11:04am UTC](https://racket.discourse.group/t/the-little-typer-implicattion-that-values-are-not-neutral/1737 "2023-08-11T11:04:33Z")
First a thanks for this great site and for your kind attention! I don't understand the conclusion of the syllogism on page 182 of the Fifth Printing of The Little Typer. It states: Variables that are not defined are n… --- ## [Error from dynamic-require collection written in typed racket in a new namespace](https://racket.discourse.group/t/error-from-dynamic-require-collection-written-in-typed-racket-in-a-new-namespace/2194)
**Author:** [@subdudu](https://racket.discourse.group/u/subdudu)\ **Replies:** 2\ **Last updated:** [August 10, 2023, 12:16am UTC](https://racket.discourse.group/t/error-from-dynamic-require-collection-written-in-typed-racket-in-a-new-namespace/2194 "2023-08-10T00:16:47Z")
I have a project, which has a main program that generates an exe file using raco exe in advance, and distributed it to clients. When the main program is running, it will dynamically require multiple compiled zo and dep f… --- ## [\`apply\` \`set-union\` in Typed Racket](https://racket.discourse.group/t/apply-set-union-in-typed-racket/2201)
**Author:** [@scolobb](https://racket.discourse.group/u/scolobb)\ **Replies:** 2\ **Last updated:** [August 9, 2023, 8:57pm UTC](https://racket.discourse.group/t/apply-set-union-in-typed-racket/2201 "2023-08-09T20:57:47Z")
Hello, I am trying to apply set-union to a list in Typed Racket. The following happily works and gives the expected answer: #lang typed/racket (apply set-union (list (set 'a 'b) (set 'c 'd))) However, if I bind the … --- ## [Shared state in a web server](https://racket.discourse.group/t/shared-state-in-a-web-server/2200)
**Author:** [@hendrikboom3](https://racket.discourse.group/u/hendrikboom3)\ **Replies:** 11\ **Last updated:** [August 9, 2023, 8:28pm UTC](https://racket.discourse.group/t/shared-state-in-a-web-server/2200 "2023-08-09T20:28:04Z")
I'm considering writing something with the structure of a multiplayer game. Server will be a network-accessible Linux box. All I can assume about the clients is that they can use reasonably modern web browsers despite … --- ## [Net/smtp sending with attachments](https://racket.discourse.group/t/net-smtp-sending-with-attachments/2181)
**Author:** [@markshead](https://racket.discourse.group/u/markshead)\ **Replies:** 1\ **Last updated:** [August 9, 2023, 1:09am UTC](https://racket.discourse.group/t/net-smtp-sending-with-attachments/2181 "2023-08-09T01:09:23Z")
I'm trying to use net/smtp to send emails that contain calendar invites. I can't seem to find a library that with let me construct the body of an email using MIME. I can probably create what I need using https://github.c… --- ## [Python string indexes](https://racket.discourse.group/t/python-string-indexes/2175)
**Author:** [@matteo-daddio](https://racket.discourse.group/u/matteo-daddio)\ **Replies:** 10\ **Last updated:** [August 7, 2023, 10:43am UTC](https://racket.discourse.group/t/python-string-indexes/2175 "2023-08-07T10:43:47Z")
Hello, I learned some Python and I discovered that it uses negative indexes when dealing with strings. Something like this: (substring “racket.discourse.group” 7 -6) =\> “discourse” (substring “racket.discourse.group”… --- ## [Racket - first language in a primary school](https://racket.discourse.group/t/racket-first-language-in-a-primary-school/2188)
**Author:** [@gour](https://racket.discourse.group/u/gour)\ **Replies:** 4\ **Last updated:** [August 2, 2023, 5:10am UTC](https://racket.discourse.group/t/racket-first-language-in-a-primary-school/2188 "2023-08-02T05:10:09Z")
Hello, I've graduated software engineering many years ago and was considering to learn & use Racket for a full-fledged desktop (GUI) application. However, due to several reasons, had to abandon the project... Our kid i… --- ## [Reading a web directory (slow) vs. reading a file (quick)](https://racket.discourse.group/t/reading-a-web-directory-slow-vs-reading-a-file-quick/2182)
**Author:** [@gknauth](https://racket.discourse.group/u/gknauth)\ **Replies:** 9\ **Last updated:** [August 1, 2023, 7:04pm UTC](https://racket.discourse.group/t/reading-a-web-directory-slow-vs-reading-a-file-quick/2182 "2023-08-01T19:04:25Z")
I'm reading a couple of NOAA directories on the web, just to find out what the latest data is. But that is taking forever, like 500 seconds (!). Whereas once I find the file I need, I can read its 28756136 bytes in 6 s… --- ## [DrRacket 8.5 glitches in combined presentation mode](https://racket.discourse.group/t/drracket-8-5-glitches-in-combined-presentation-mode/2161)
**Author:** [@srikumarks](https://racket.discourse.group/u/srikumarks)\ **Replies:** 5\ **Last updated:** [August 1, 2023, 1:16pm UTC](https://racket.discourse.group/t/drracket-8-5-glitches-in-combined-presentation-mode/2161 "2023-08-01T13:16:10Z")
Hi Racketeers, I'm using DrRacket in class where it is full screen on my laptop, being projected to students in class and also shared with online attendees via Zoom screenshare (I teach CS at Krea University). In this … --- ## [Making nested vectors with build-vector in typed/racket](https://racket.discourse.group/t/making-nested-vectors-with-build-vector-in-typed-racket/2183)
**Author:** [@srikumarks](https://racket.discourse.group/u/srikumarks)\ **Replies:** 4\ **Last updated:** [August 1, 2023, 4:22am UTC](https://racket.discourse.group/t/making-nested-vectors-with-build-vector-in-typed-racket/2183 "2023-08-01T04:22:23Z")
I can't seem to get how to get the use of build-vector in the following code to pass the Racket type checker. I've reduced this from an existing untyped function that constructs an "image" as a "vector of vector of color… --- ## [Trying the PLT Games collection?](https://racket.discourse.group/t/trying-the-plt-games-collection/2156)
**Author:** [@late\_bloomer](https://racket.discourse.group/u/late_bloomer)\ **Replies:** 3\ **Last updated:** [July 27, 2023, 6:36pm UTC](https://racket.discourse.group/t/trying-the-plt-games-collection/2156 "2023-07-27T18:36:22Z")
\[Solved\] Sorry about all this. I just needed to stick with the name of the package actually shown in the list of installed ones (so "games" instead of plt-games), and not add anything beyond (require games), before I run… --- ## [Best way of drawing with turtles](https://racket.discourse.group/t/best-way-of-drawing-with-turtles/2166)
**Author:** [@absalom](https://racket.discourse.group/u/absalom)\ **Replies:** 9\ **Last updated:** [July 27, 2023, 5:23pm UTC](https://racket.discourse.group/t/best-way-of-drawing-with-turtles/2166 "2023-07-27T17:23:18Z")
Hi, I have to teach functional programming and I chose Scheme as the main language I will use for that course. I chose DrRacket as the IDE my students will use for obvious practical reasons. I will stick to R5RS and wil… [Previous page](https://racket.discourse.group/c/questions/6.md?page=18) [Next page](https://racket.discourse.group/c/questions/6.md?page=20)