# Questions & Answers

**URL:** https://racket.discourse.group/c/questions/6.md?page=20

[Latest](https://racket.discourse.group/latest.md) · [Categories](https://racket.discourse.group/categories.md) · [Tags](https://racket.discourse.group/tags.md)

**Page:** 21

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## [Struggling with trivial command line program](https://racket.discourse.group/t/struggling-with-trivial-command-line-program/2152)

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**Author:** [@lewisl](https://racket.discourse.group/u/lewisl)\
**Replies:** 2\
**Last updated:** [July 24, 2023, 12:48am UTC](https://racket.discourse.group/t/struggling-with-trivial-command-line-program/2152 "2023-07-24T00:48:14Z")

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Both versions work. Which would you use? It's surprising how hard this is and how inconsistent across schemes (and, of course, common lisp). Which would you use? #lang cli (program (square n) (let ((num (string-\>n…

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## [Closing DrRacket 8.9 takes time](https://racket.discourse.group/t/closing-drracket-8-9-takes-time/2151)

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**Author:** [@joskoot](https://racket.discourse.group/u/joskoot)\
**Replies:** 0\
**Last updated:** [July 23, 2023, 4:31pm UTC](https://racket.discourse.group/t/closing-drracket-8-9-takes-time/2151 "2023-07-23T16:31:29Z")

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Closing DrRacket 8.9 (both BC and cs) may take up to a second. Not a big problem, of course, but I wonder what DrRacket is doing in that time.

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## [\#lang cli doesn't work or no longer is part of Racket](https://racket.discourse.group/t/lang-cli-doesnt-work-or-no-longer-is-part-of-racket/2137)

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**Author:** [@lewisl](https://racket.discourse.group/u/lewisl)\
**Replies:** 2\
**Last updated:** [July 22, 2023, 11:19pm UTC](https://racket.discourse.group/t/lang-cli-doesnt-work-or-no-longer-is-part-of-racket/2137 "2023-07-22T23:19:56Z")

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I followed an example in the doc: In order to use the language to write a command line script, simply declare the module as #lang cli at the top of the file. #lang cli (program (hello name) (displayln (string-appen…

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## [How hard would it be to build a api as a service company using racket?](https://racket.discourse.group/t/how-hard-would-it-be-to-build-a-api-as-a-service-company-using-racket/2115)

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**Author:** [@Jobhdez](https://racket.discourse.group/u/Jobhdez)\
**Replies:** 2\
**Last updated:** [July 21, 2023, 12:46am UTC](https://racket.discourse.group/t/how-hard-would-it-be-to-build-a-api-as-a-service-company-using-racket/2115 "2023-07-21T00:46:23Z")

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hey, I have always gotten excited about starting a company with lisp or haskell. Was wondering if it would be a good decision choosing racket if I happen to start something. thanks

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## [Surprising (?) type error](https://racket.discourse.group/t/surprising-type-error/2110)

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**Author:** [@bkc39](https://racket.discourse.group/u/bkc39)\
**Replies:** 1\
**Last updated:** [July 18, 2023, 4:58pm UTC](https://racket.discourse.group/t/surprising-type-error/2110 "2023-07-18T16:58:42Z")

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I have been going through the typed/racket guide and encountered code like the following #lang typed/racket (: prop:foo (Struct-Property (-\> Self Number))) (: foo-pred (-\> Any Boolean : (Has-Struct-Property prop:foo)))…

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## [How to add a search box to a scrrible document](https://racket.discourse.group/t/how-to-add-a-search-box-to-a-scrrible-document/2112)

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**Author:** [@jmj](https://racket.discourse.group/u/jmj)\
**Replies:** 4\
**Last updated:** [July 18, 2023, 3:13pm UTC](https://racket.discourse.group/t/how-to-add-a-search-box-to-a-scrrible-document/2112 "2023-07-18T15:13:14Z")

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Hello everyone, I am making study notes with scrrible. I hope the notes can be searched, just like Racket documents. How to do that?

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## [Scheme and concurrent programming](https://racket.discourse.group/t/scheme-and-concurrent-programming/2102)

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**Author:** [@matteo-daddio](https://racket.discourse.group/u/matteo-daddio)\
**Replies:** 3\
**Last updated:** [July 15, 2023, 3:59pm UTC](https://racket.discourse.group/t/scheme-and-concurrent-programming/2102 "2023-07-15T15:59:56Z")

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Hello, I don’t know if this is the right place to ask, but why scheme doesn’t support concurrent programming? Matteo

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## [GUI in sandbox not working](https://racket.discourse.group/t/gui-in-sandbox-not-working/2090)

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**Author:** [@Erich](https://racket.discourse.group/u/Erich)\
**Replies:** 3\
**Last updated:** [July 13, 2023, 6:39pm UTC](https://racket.discourse.group/t/gui-in-sandbox-not-working/2090 "2023-07-13T18:39:05Z")

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I'm still trying to get my plugin system working (Racket plugins in a Golang application). The problem is that it does work for ordinary code, but it does not seem to work for GUI. The gracket executable is started as a …

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## [Links in scribble to rkt files and the like](https://racket.discourse.group/t/links-in-scribble-to-rkt-files-and-the-like/2096)

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**Author:** [@joskoot](https://racket.discourse.group/u/joskoot)\
**Replies:** 2\
**Last updated:** [July 13, 2023, 6:18am UTC](https://racket.discourse.group/t/links-in-scribble-to-rkt-files-and-the-like/2096 "2023-07-13T06:18:21Z")

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In a scribble file (especially scribble/manual) I include hyperlinks to .rkt files and alike. However, clicking a link opens the file in the browser, it does not open it with DrRacket. This problem does not occur in .doc…

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## [Which to read first PLAI or EOPL?](https://racket.discourse.group/t/which-to-read-first-plai-or-eopl/2087)

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**Author:** [@matteo-daddio](https://racket.discourse.group/u/matteo-daddio)\
**Replies:** 2\
**Last updated:** [July 10, 2023, 11:43pm UTC](https://racket.discourse.group/t/which-to-read-first-plai-or-eopl/2087 "2023-07-10T23:43:57Z")

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Hello, I’m reading PLAI. It’s better to read PLAI first and then EOPL or the contrary? In racket documentation EOPL is listed first. Matteo

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## [Question regarding head patterns in macros generating macros](https://racket.discourse.group/t/question-regarding-head-patterns-in-macros-generating-macros/2088)

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**Author:** [@jschappel](https://racket.discourse.group/u/jschappel)\
**Replies:** 1\
**Last updated:** [July 10, 2023, 6:56pm UTC](https://racket.discourse.group/t/question-regarding-head-patterns-in-macros-generating-macros/2088 "2023-07-10T18:56:18Z")

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Hello :wave:! I am messing around with racket macros and I have a question regarding macros generating macros. I originally created a simple macro that creates a local binding which allows rackets define syntax and limit…

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## [Copy/paste from scribble/acmart @sigplan into DrRacket?](https://racket.discourse.group/t/copy-paste-from-scribble-acmart-sigplan-into-drracket/2078)

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**Author:** [@benknoble](https://racket.discourse.group/u/benknoble)\
**Replies:** 14\
**Last updated:** [July 8, 2023, 3:38pm UTC](https://racket.discourse.group/t/copy-paste-from-scribble-acmart-sigplan-into-drracket/2078 "2023-07-08T15:38:49Z")

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This should be a short example document that produces the problem: #lang scribble/acmart @sigplan @screen @(require scriblib/figure (only-in scribble/manual racketmod0)) @title{Title} @section{Section} @fi…

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## [Modifying bindings in modules in \*SL](https://racket.discourse.group/t/modifying-bindings-in-modules-in-sl/2077)

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**Author:** [@dbp](https://racket.discourse.group/u/dbp)\
**Replies:** 2\
**Last updated:** [July 7, 2023, 5:01pm UTC](https://racket.discourse.group/t/modifying-bindings-in-modules-in-sl/2077 "2023-07-07T17:01:04Z")

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I'm working on a library that implements Jack Wrenn's Dissertation work (https://jack.wrenn.fyi/publications/dissertation.pdf) -- essentially, taking student test suites and running them against known good and bad implem…

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## [How to create the most permissive security guard for a racket sandbox?](https://racket.discourse.group/t/how-to-create-the-most-permissive-security-guard-for-a-racket-sandbox/2071)

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**Author:** [@Erich](https://racket.discourse.group/u/Erich)\
**Replies:** 4\
**Last updated:** [July 6, 2023, 1:01pm UTC](https://racket.discourse.group/t/how-to-create-the-most-permissive-security-guard-for-a-racket-sandbox/2071 "2023-07-06T13:01:49Z")

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Hi folks! For a plugin/bridge system with a Go program, I'm using make-evaluator from sandbox but for the time being would like to allow the full racket/gui language with access to any file. So I'm using this: (sandbox-…

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## [Racket installation with Nix (Newbie)](https://racket.discourse.group/t/racket-installation-with-nix-newbie/2069)

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**Author:** [@maddalab](https://racket.discourse.group/u/maddalab)\
**Replies:** 5\
**Last updated:** [July 5, 2023, 3:01pm UTC](https://racket.discourse.group/t/racket-installation-with-nix-newbie/2069 "2023-07-05T15:01:34Z")

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Hello, Complete noob here, learning both nix and starting racket at the same time - might not be a good idea. I installed Racket using nix, below is my derivation to install it let pkgs = import \<nixpkgs\> { }; in pk…

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## [SICP in Racket documentation](https://racket.discourse.group/t/sicp-in-racket-documentation/2037)

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**Author:** [@matteo-daddio](https://racket.discourse.group/u/matteo-daddio)\
**Replies:** 21\
**Last updated:** [July 3, 2023, 12:00pm UTC](https://racket.discourse.group/t/sicp-in-racket-documentation/2037 "2023-07-03T12:00:41Z")

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Hello, I noticed that SICP isn’t mentioned in Racket documentation near the other textbook like PLAI and EOPL. I wonder why.

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## [Class contract on abstract method](https://racket.discourse.group/t/class-contract-on-abstract-method/2052)

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**Author:** [@madkins23](https://racket.discourse.group/u/madkins23)\
**Replies:** 1\
**Last updated:** [June 28, 2023, 11:59pm UTC](https://racket.discourse.group/t/class-contract-on-abstract-method/2052 "2023-06-28T23:59:47Z")

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In the following example code: #lang racket/base (require racket/class racket/contract) (define/contract parent% (class/c (override \[meth (-\>m string? void?)\])) (class object% (super-new) (abstract met…

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## [How to declare compilation dependencies manually?](https://racket.discourse.group/t/how-to-declare-compilation-dependencies-manually/2049)

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**Author:** [@shhyou](https://racket.discourse.group/u/shhyou)\
**Replies:** 1\
**Last updated:** [June 28, 2023, 1:11pm UTC](https://racket.discourse.group/t/how-to-declare-compilation-dependencies-manually/2049 "2023-06-28T13:11:13Z")

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How can I declare a (module) dependency manually without requireing it? I have found the function register-external-module, but it only adds an additional dependency after the code has been compiled. In other words, the…

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## [Software freedom conservancy](https://racket.discourse.group/t/software-freedom-conservancy/2035)

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**Author:** [@matteo-daddio](https://racket.discourse.group/u/matteo-daddio)\
**Replies:** 8\
**Last updated:** [June 27, 2023, 7:50am UTC](https://racket.discourse.group/t/software-freedom-conservancy/2035 "2023-06-27T07:50:28Z")

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Hello, I noticed that Racket is member of SFC. I wonder what are the differences between SFC and FSF.

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## [How to turn off highlighting in DrRacket](https://racket.discourse.group/t/how-to-turn-off-highlighting-in-drracket/2041)

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**Author:** [@Watt](https://racket.discourse.group/u/Watt)\
**Replies:** 3\
**Last updated:** [June 26, 2023, 3:25pm UTC](https://racket.discourse.group/t/how-to-turn-off-highlighting-in-drracket/2041 "2023-06-26T15:25:09Z")

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I've just started using DrRacket. When I type a closing parenthesis, the opening one is highlighted in blue for maybe a second or half a second. When my cursor is at the end of a parenthesis, there is a grey background f…

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## [How to include a Google analytics tag to a scribble website](https://racket.discourse.group/t/how-to-include-a-google-analytics-tag-to-a-scribble-website/2042)

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**Author:** [@Panadestein](https://racket.discourse.group/u/Panadestein)\
**Replies:** 1\
**Last updated:** [June 26, 2023, 9:08am UTC](https://racket.discourse.group/t/how-to-include-a-google-analytics-tag-to-a-scribble-website/2042 "2023-06-26T09:08:11Z")

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I would like to add a Google Analytics tag to a scribble generated website. I have found this solution here, but it is outdated. The new form of the tags is: \<!-- Google tag (gtag.js) --\> \<script async src="https://www.…

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## [Require: namespace mismatch](https://racket.discourse.group/t/require-namespace-mismatch/2016)

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**Author:** [@madkins23](https://racket.discourse.group/u/madkins23)\
**Replies:** 5\
**Last updated:** [June 22, 2023, 11:49pm UTC](https://racket.discourse.group/t/require-namespace-mismatch/2016 "2023-06-22T23:49:04Z")

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I've now ended up in this situation twice: require: namespace mismatch; reference to a module that is not instantiated module: "/usr/local/racket/share/pkgs/drracket/drracket/private/drracket-errortrace-key.rkt" ph…

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## [Pollen's define-meta isn't working, get-template-for ignores it](https://racket.discourse.group/t/pollens-define-meta-isnt-working-get-template-for-ignores-it/2028)

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**Author:** [@kurinoku](https://racket.discourse.group/u/kurinoku)\
**Replies:** 3\
**Last updated:** [June 22, 2023, 1:59pm UTC](https://racket.discourse.group/t/pollens-define-meta-isnt-working-get-template-for-ignores-it/2028 "2023-06-22T13:59:19Z")

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I'm using pollen, I have this directory setup . |- template.html.p |- template.html |- topic-welcome.html |- topic-welcome.html.p |- subdir | |- index.poly.p index.poly.p contents are #lang pollen ◊(define-meta temp…

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## [Italian keyboard](https://racket.discourse.group/t/italian-keyboard/2034)

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**Author:** [@matteo-daddio](https://racket.discourse.group/u/matteo-daddio)\
**Replies:** 2\
**Last updated:** [June 22, 2023, 11:14am UTC](https://racket.discourse.group/t/italian-keyboard/2034 "2023-06-22T11:14:17Z")

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Hello, I’m Italian and I use an Italian keyboard. In Italian keyboards there isn’t { and } keys, but in windows and Linux there’s a way to enter them. This is my Italian keyboard. If I press alt gr + shift + è the…

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## [Question About Macro Bindings](https://racket.discourse.group/t/question-about-macro-bindings/2033)

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**Author:** [@jschappel](https://racket.discourse.group/u/jschappel)\
**Replies:** 6\
**Last updated:** [June 21, 2023, 3:50pm UTC](https://racket.discourse.group/t/question-about-macro-bindings/2033 "2023-06-21T15:50:06Z")

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Hello :wave:! I am tying to write 2 simple macros where one renames a identifier by appending $ to the beginning and end. The other returns the newly created identifiers in a list. #lang racket (require (for-syntax syn…

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## [Frames and Displays](https://racket.discourse.group/t/frames-and-displays/2026)

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**Author:** [@madkins23](https://racket.discourse.group/u/madkins23)\
**Replies:** 12\
**Last updated:** [June 21, 2023, 2:47pm UTC](https://racket.discourse.group/t/frames-and-displays/2026 "2023-06-21T14:47:07Z")

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I have a two-display configuration running on Ubuntu Linux. My "main" screen is my laptop but the screen I usually "use" is a secondary, larger monitor that sits right in front of me. I have the launcher bar configured t…

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## [Plugins killed double-click behavior in DrRacket?](https://racket.discourse.group/t/plugins-killed-double-click-behavior-in-drracket/2013)

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**Author:** [@madkins23](https://racket.discourse.group/u/madkins23)\
**Replies:** 1\
**Last updated:** [June 17, 2023, 9:34pm UTC](https://racket.discourse.group/t/plugins-killed-double-click-behavior-in-drracket/2013 "2023-06-17T21:34:49Z")

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Not so much a question... I lost the double-click behavior (selection of symbol under cursor) in DrRacket somehow and had to completely reload Racket/DrRacket to get it back. I think that it happened when I loaded two …

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## [Eval seems to behave differently in typed and untyped racket](https://racket.discourse.group/t/eval-seems-to-behave-differently-in-typed-and-untyped-racket/2020)

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**Author:** [@wurmli](https://racket.discourse.group/u/wurmli)\
**Replies:** 0\
**Last updated:** [June 16, 2023, 5:35pm UTC](https://racket.discourse.group/t/eval-seems-to-behave-differently-in-typed-and-untyped-racket/2020 "2023-06-16T17:35:07Z")

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My problem looks the same as Provide an example using “eval-syntax” & “syntax” in typed/racket, but isn't reading/parsing and type-checking going on at the same time? Or, doesn't this behaviour break the Scheme motto tha…

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## [Sequences vs. streams](https://racket.discourse.group/t/sequences-vs-streams/1987)

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**Author:** [@sschwarzer](https://racket.discourse.group/u/sschwarzer)\
**Replies:** 11\
**Last updated:** [June 15, 2023, 7:11pm UTC](https://racket.discourse.group/t/sequences-vs-streams/1987 "2023-06-15T19:11:21Z")

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I read the Racket Reference sections about sequences and streams and am a bit confused. I have a few questions: Why does Racket have sequences and streams? Conceptually, they seem the same. Also, it's possible to con…

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## [Predicate to check for \`(values)\`?](https://racket.discourse.group/t/predicate-to-check-for-values/2012)

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**Author:** [@sschwarzer](https://racket.discourse.group/u/sschwarzer)\
**Replies:** 4\
**Last updated:** [June 15, 2023, 8:53am UTC](https://racket.discourse.group/t/predicate-to-check-for-values/2012 "2023-06-15T08:53:52Z")

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If I define a generator (require racket/generator) (define a-generator (generator () (yield 1) (yield 2))) and call a-generator repeatedly, I get \> (a-generator) 1 \> (a-generator) 2 \> (a-generator) \> (a-gen…

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