# Latest

**URL:** https://discourse.haskell.org/latest.md?page=8

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

**Page:** 9

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## [\[ANN\] Fourmolu 0.20.0.0 released](https://discourse.haskell.org/t/ann-fourmolu-0-20-0-0-released/14288)

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**Author:** [@brandonchinn178](https://discourse.haskell.org/u/brandonchinn178)\
**Replies:** 1\
**Last updated:** [June 19, 2026, 10:30am UTC](https://discourse.haskell.org/t/ann-fourmolu-0-20-0-0-released/14288 "2026-06-19T10:30:17Z")

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Fourmolu is a Haskell formatter. 0.20 comes with a couple fixes + new options, plus support for GHC 9.14. It’s also the first version to be installable with ghcup! ghcup config add-release-channel 3rdparty ghcup insta…

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## [Release \`language-haskell\` 3.8.0](https://discourse.haskell.org/t/release-language-haskell-3-8-0/14275)

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**Author:** [@fendor](https://discourse.haskell.org/u/fendor)\
**Replies:** 8\
**Last updated:** [June 19, 2026, 9:53am UTC](https://discourse.haskell.org/t/release-language-haskell-3-8-0/14275 "2026-06-19T09:53:58Z")

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The Haskell IDE team is excited to announce a new the first release of language-haskell under the Haskell community namespace. The extension language-haskell has served the community well and for a long time! Now, it wa…

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## [Config languages (and Dhall)](https://discourse.haskell.org/t/config-languages-and-dhall/13948)

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**Author:** [@hasufell](https://discourse.haskell.org/u/hasufell)\
**Replies:** 28\
**Last updated:** [June 18, 2026, 8:09pm UTC](https://discourse.haskell.org/t/config-languages-and-dhall/13948 "2026-06-18T20:09:00Z")

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I’ve been tinkering with Dhall in GHCup: ghcup-metadata/dhall at installer-dsl · haskell/ghcup-metadata · GitHub But my feeling was it is not a good fit: no text comparison updating deeply nested Maps is very hard syn…

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## [GHC musl docker manifests: Base image updated to alpine:3.24](https://discourse.haskell.org/t/ghc-musl-docker-manifests-base-image-updated-to-alpine-3-24/14289)

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**Author:** [@benz0li](https://discourse.haskell.org/u/benz0li)\
**Replies:** 0\
**Last updated:** [June 18, 2026, 7:26pm UTC](https://discourse.haskell.org/t/ghc-musl-docker-manifests-base-image-updated-to-alpine-3-24/14289 "2026-06-18T19:26:56Z")

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The following GHC musl docker manifests have been updated to alpine:3.24. Available from Quay: quay.io/benz0li/ghc-musl:9.14.1 quay.io/benz0li/ghc-musl:9.14.1-int-native quay.io/benz0li/ghc-musl:9.12.4 quay.io/benz0li…

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## [Nix for Haskell: Static Builds](https://discourse.haskell.org/t/nix-for-haskell-static-builds/14287)

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**Author:** [@abhin4v](https://discourse.haskell.org/u/abhin4v)\
**Replies:** 0\
**Last updated:** [June 18, 2026, 3:10pm UTC](https://discourse.haskell.org/t/nix-for-haskell-static-builds/14287 "2026-06-18T15:10:53Z")

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## [Haskell's missing mutable reference type](https://discourse.haskell.org/t/haskells-missing-mutable-reference-type/14248)

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**Author:** [@tomjaguarpaw](https://discourse.haskell.org/u/tomjaguarpaw)\
**Replies:** 63\
**Last updated:** [June 18, 2026, 10:53am UTC](https://discourse.haskell.org/t/haskells-missing-mutable-reference-type/14248 "2026-06-18T10:53:03Z")

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Whilst looking at the Scoped thread-locals GHC proposal I realised that Haskell is missing a mutable reference type that some other languges have (and people have tried to encode in Haskell), so I wrote it up: haskells…

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## [Specialization and dead code elimination](https://discourse.haskell.org/t/specialization-and-dead-code-elimination/14283)

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**Author:** [@mkleczek](https://discourse.haskell.org/u/mkleczek)\
**Replies:** 1\
**Last updated:** [June 17, 2026, 5:28pm UTC](https://discourse.haskell.org/t/specialization-and-dead-code-elimination/14283 "2026-06-17T17:28:54Z")

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Hi All, I am struggling with code optimization. I have a polymorphic function fun in module A that is only used in module B. Adding -fexpose-overloaded-unfoldings -fspecialise-aggressively caused GHC to generate a spec…

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## [Implementing Redis INFO in Haskell](https://discourse.haskell.org/t/implementing-redis-info-in-haskell/14284)

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**Author:** [@OlaoluwaM](https://discourse.haskell.org/u/OlaoluwaM)\
**Replies:** 0\
**Last updated:** [June 17, 2026, 4:48pm UTC](https://discourse.haskell.org/t/implementing-redis-info-in-haskell/14284 "2026-06-17T16:48:51Z")

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Wrote about adding support for the INFO command to my Redis server. Let me know what you think!

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## [\[ANN\] Hpack-Dhall with Cabal commands](https://discourse.haskell.org/t/ann-hpack-dhall-with-cabal-commands/14282)

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**Author:** [@philderbeast](https://discourse.haskell.org/u/philderbeast)\
**Replies:** 0\
**Last updated:** [June 17, 2026, 3:06pm UTC](https://discourse.haskell.org/t/ann-hpack-dhall-with-cabal-commands/14282 "2026-06-17T15:06:20Z")

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I’ve made a new release of Hpack-Dhall, hpack-dhall-0.6.0. Hpack-Dhall is like Hpack but with the “functions + types + imports” of Dhall. There’s a new user guide at Hpack⩓Dhall and this release adds cabal ypack and caba…

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## [Best way to run tests on file save](https://discourse.haskell.org/t/best-way-to-run-tests-on-file-save/14264)

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**Author:** [@marcosh](https://discourse.haskell.org/u/marcosh)\
**Replies:** 7\
**Last updated:** [June 17, 2026, 10:49am UTC](https://discourse.haskell.org/t/best-way-to-run-tests-on-file-save/14264 "2026-06-17T10:49:47Z")

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TL;DR: what is the best way to run tests on every file save? On the project we have at work, I’d like to run the test suite at every file save. At the moment I’m doing it using stack test --file-watch. This works but it…

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## [Optimizing interpreted code](https://discourse.haskell.org/t/optimizing-interpreted-code/14281)

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**Author:** [@mchav](https://discourse.haskell.org/u/mchav)\
**Replies:** 2\
**Last updated:** [June 17, 2026, 3:27am UTC](https://discourse.haskell.org/t/optimizing-interpreted-code/14281 "2026-06-17T03:27:32Z")

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Looking into options for making GHCi run faster and came across: 3. Using GHCi — Glasgow Haskell Compiler 9.15.20260306 User's Guide Before GHC 9.8, optimizations were considered too unstable to be used with the byteco…

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## [Contributing to Haskell Through a Beginner’s Lens](https://discourse.haskell.org/t/contributing-to-haskell-through-a-beginner-s-lens/14278)

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**Author:** [@Kleidukos](https://discourse.haskell.org/u/Kleidukos)\
**Replies:** 0\
**Last updated:** [June 16, 2026, 4:27pm UTC](https://discourse.haskell.org/t/contributing-to-haskell-through-a-beginner-s-lens/14278 "2026-06-16T16:27:42Z")

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After becoming a regular contributor to haskell-language-server and even having his Google Summer of Code proposal accepted, Vidit wanted to talk about his experience on approaching Haskell code bases. This is “Contribu…

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## [Vladislav Zavialov on Dependent Haskell - Type Theory Forall Podcast](https://discourse.haskell.org/t/vladislav-zavialov-on-dependent-haskell-type-theory-forall-podcast/14277)

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**Author:** [@jaror](https://discourse.haskell.org/u/jaror)\
**Replies:** 1\
**Last updated:** [June 16, 2026, 2:27pm UTC](https://discourse.haskell.org/t/vladislav-zavialov-on-dependent-haskell-type-theory-forall-podcast/14277 "2026-06-16T14:27:18Z")

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## [Boulder, Colorado Haskell Meetup (on Zoom) – Tues, June 16](https://discourse.haskell.org/t/boulder-colorado-haskell-meetup-on-zoom-tues-june-16/14273)

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**Author:** [@sellout](https://discourse.haskell.org/u/sellout)\
**Replies:** 1\
**Last updated:** [June 16, 2026, 10:22am UTC](https://discourse.haskell.org/t/boulder-colorado-haskell-meetup-on-zoom-tues-june-16/14273 "2026-06-16T10:22:25Z")

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This month Greg Pfeil (that’s me) will give a recap of ZuriHac – talks, projects, hallway track, etc. You’ll feel like you were there (or maybe at least wish you had been). It’s on Zoom, so feel free to join from anywhe…

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## [\[ANN\] tricorder - a new development tool for Haskell and LLMs](https://discourse.haskell.org/t/ann-tricorder-a-new-development-tool-for-haskell-and-llms/14208)

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**Author:** [@cgeorgii](https://discourse.haskell.org/u/cgeorgii)\
**Replies:** 12\
**Last updated:** [June 16, 2026, 3:36am UTC](https://discourse.haskell.org/t/ann-tricorder-a-new-development-tool-for-haskell-and-llms/14208 "2026-06-16T03:36:02Z")

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Hey everyone, for those of you who don’t know me, my name is Christian and I’m an engineer at Tweag. I am very pleased to announce the very first release of tricorder! :tada: tricorder has been my daily driver for Has…

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## [Haskell Interlude #83: POPL 2026 - Part 2](https://discourse.haskell.org/t/haskell-interlude-83-popl-2026-part-2/14274)

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**Author:** [@sperber](https://discourse.haskell.org/u/sperber)\
**Replies:** 0\
**Last updated:** [June 15, 2026, 6:21am UTC](https://discourse.haskell.org/t/haskell-interlude-83-popl-2026-part-2/14274 "2026-06-15T06:21:25Z")

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Today’s Interlude is the second part of a miniseries on this year’s Symposium on Principles of Programming Languages, a.k.a. POPL 2026, hosted by Jessica Foster. In this episode we talk about: symbolic execution monads,…

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## [The Hazy Haskell Compiler](https://discourse.haskell.org/t/the-hazy-haskell-compiler/13497)

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**Author:** [@superstar64](https://discourse.haskell.org/u/superstar64)\
**Replies:** 30\
**Last updated:** [June 14, 2026, 3:35pm UTC](https://discourse.haskell.org/t/the-hazy-haskell-compiler/13497 "2026-06-14T15:35:36Z")

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I’m proud to showcase Hazy, my Haskell compiler. This is a project I have been working on in private for 3 years. It’s unfortunately not finished but it’s at the point where it’s fairly interesting. The type checker larg…

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## [Sabela Notebook Gallery](https://discourse.haskell.org/t/sabela-notebook-gallery/14271)

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**Author:** [@mchav](https://discourse.haskell.org/u/mchav)\
**Replies:** 2\
**Last updated:** [June 14, 2026, 1:36pm UTC](https://discourse.haskell.org/t/sabela-notebook-gallery/14271 "2026-06-14T13:36:36Z")

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Thanks to @tomjaguarpaw and @hungryjoe for contributing. If anyone has any tutorial or script that they’d like to showcase let me know.

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## [Fork-fragile reader-like operations in Haskell](https://discourse.haskell.org/t/fork-fragile-reader-like-operations-in-haskell/14258)

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**Author:** [@tomjaguarpaw](https://discourse.haskell.org/u/tomjaguarpaw)\
**Replies:** 8\
**Last updated:** [June 14, 2026, 10:22am UTC](https://discourse.haskell.org/t/fork-fragile-reader-like-operations-in-haskell/14258 "2026-06-14T10:22:45Z")

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Following up from Haskell's missing mutable reference type and A reference implementation of IOScopedRef comes the final instalment in the series: Fork-fragile reader-like operations in Haskell

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## [What is a higher-order effect?](https://discourse.haskell.org/t/what-is-a-higher-order-effect/10744)

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**Author:** [@tomjaguarpaw](https://discourse.haskell.org/u/tomjaguarpaw)\
**Replies:** 33\
**Last updated:** [June 13, 2026, 2:21pm UTC](https://discourse.haskell.org/t/what-is-a-higher-order-effect/10744 "2026-06-13T14:21:40Z")

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Via a comment of @arybczak, I came to this example of an effectful higher-order effect: ▶ Preamble example :: IO () example = runEff $ runReader "global" $ do interpret (\\\_ SomeAction -\> (liftIO . putStrLn) =\<…

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## [Narrowing range of GHCs able to build Cabal](https://discourse.haskell.org/t/narrowing-range-of-ghcs-able-to-build-cabal/14269)

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**Author:** [@Bodigrim](https://discourse.haskell.org/u/Bodigrim)\
**Replies:** 0\
**Last updated:** [June 12, 2026, 6:39pm UTC](https://discourse.haskell.org/t/narrowing-range-of-ghcs-able-to-build-cabal/14269 "2026-06-12T18:39:01Z")

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Cabal project narrows the range of GHCs able to build Cabal-syntax, Cabal, cabal-install-solver, cabal-install, etc. to support 3 years worth of compilers, which currently spans back to GHC 9.4. To avoid ambiguity: as o…

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## ["I built a web language with Haskell-like syntax for fun](https://discourse.haskell.org/t/i-built-a-web-language-with-haskell-like-syntax-for-fun/14214)

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**Author:** [@Atom1cB1rd](https://discourse.haskell.org/u/Atom1cB1rd)\
**Replies:** 10\
**Last updated:** [June 12, 2026, 6:09pm UTC](https://discourse.haskell.org/t/i-built-a-web-language-with-haskell-like-syntax-for-fun/14214 "2026-06-12T18:09:36Z")

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I’ve been building a web language with Haskell-like syntax and a PHP-like execution model server/client separation in the same file. It’s not complete but it’s functional. Built it mostly for fun rather than to solve any…

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## [New tutorial series on implementing lambda calculus interpreter in Я](https://discourse.haskell.org/t/new-tutorial-series-on-implementing-lambda-calculus-interpreter-in/14268)

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**Author:** [@iokasimov](https://discourse.haskell.org/u/iokasimov)\
**Replies:** 0\
**Last updated:** [June 12, 2026, 3:46pm UTC](https://discourse.haskell.org/t/new-tutorial-series-on-implementing-lambda-calculus-interpreter-in/14268 "2026-06-12T15:46:52Z")

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First three chapters with a fresh look on how to work with AST using functors and natural transformations: https://muratkasimov.art/Ya/Tutorials/Lambda-calculus-interpreter-1/ https://muratkasimov.art/Ya/Tutorials/Lamb…

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## [Blog: Haskell for Elm developers, Part 8 — IO](https://discourse.haskell.org/t/blog-haskell-for-elm-developers-part-8-io/14267)

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**Author:** [@kutyel](https://discourse.haskell.org/u/kutyel)\
**Replies:** 0\
**Last updated:** [June 12, 2026, 2:13pm UTC](https://discourse.haskell.org/t/blog-haskell-for-elm-developers-part-8-io/14267 "2026-06-12T14:13:23Z")

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Latest in my series teaching Haskell via Elm concepts. This one explains IO through Task/Cmd: descriptions of effects, composed monadically, run only at the main boundary. Includes an honest look at where the analogy bre…

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## [Release \`vscode-haskell\` 2.8.1](https://discourse.haskell.org/t/release-vscode-haskell-2-8-1/14266)

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**Author:** [@fendor](https://discourse.haskell.org/u/fendor)\
**Replies:** 0\
**Last updated:** [June 12, 2026, 1:53pm UTC](https://discourse.haskell.org/t/release-vscode-haskell-2-8-1/14266 "2026-06-12T13:53:44Z")

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vscode-haskell 2.8.1 The HLS team announces a new release for the vscode-haskell extension. Important bug fix We drop the explicit dependency on language-haskell to unblock people stuck on Cannot activate extension due …

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## [\[ANN\] hpgsql, a pure Haskell PostgreSQL driver (no libpq)](https://discourse.haskell.org/t/ann-hpgsql-a-pure-haskell-postgresql-driver-no-libpq/14101)

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**Author:** [@mzabani](https://discourse.haskell.org/u/mzabani)\
**Replies:** 14\
**Last updated:** [June 11, 2026, 8:11pm UTC](https://discourse.haskell.org/t/ann-hpgsql-a-pure-haskell-postgresql-driver-no-libpq/14101 "2026-06-11T20:11:14Z")

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It’s a pleasure to announce hpgsql, a PostgreSQL driver written in pure Haskell (no libpq), with an API largely inspired by the great postgresql-simple library, but featuring: Usage of PostgreSQL’s binary protocol Quer…

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## [\[ANN\] Stack 3.9.3](https://discourse.haskell.org/t/ann-stack-3-9-3/13702)

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**Author:** [@mpilgrem](https://discourse.haskell.org/u/mpilgrem)\
**Replies:** 4\
**Last updated:** [June 11, 2026, 6:50pm UTC](https://discourse.haskell.org/t/ann-stack-3-9-3/13702 "2026-06-11T18:50:47Z")

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See https://haskellstack.org/ for installation and upgrade instructions. Release notes: This release fixes a potential bug for users of Stack’s Docker integration. Changes since v3.9.1: Other enhancements: The r…

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## [Issue 528 :: Haskell Weekly newsletter](https://discourse.haskell.org/t/issue-528-haskell-weekly-newsletter/14263)

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**Author:** [@taylorfausak](https://discourse.haskell.org/u/taylorfausak)\
**Replies:** 0\
**Last updated:** [June 11, 2026, 6:02pm UTC](https://discourse.haskell.org/t/issue-528-haskell-weekly-newsletter/14263 "2026-06-11T18:02:25Z")

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## [\[ANN\] GHCup 0.2.2.0 release](https://discourse.haskell.org/t/ann-ghcup-0-2-2-0-release/14144)

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**Author:** [@hasufell](https://discourse.haskell.org/u/hasufell)\
**Replies:** 5\
**Last updated:** [June 11, 2026, 5:14pm UTC](https://discourse.haskell.org/t/ann-ghcup-0-2-2-0-release/14144 "2026-06-11T17:14:14Z")

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I’m very pleased to announce the release of :tada: 0.2.2.0 :tada: :flexed\_biceps: Motivation The work on this release was sponsored by IOG, since their need for shipping alternative compilers coincided with the Installe…

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## [H2JVM - A Haskell Library for writing JVM Bytecode](https://discourse.haskell.org/t/h2jvm-a-haskell-library-for-writing-jvm-bytecode/14182)

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**Author:** [@bristermitten](https://discourse.haskell.org/u/bristermitten)\
**Replies:** 19\
**Last updated:** [June 10, 2026, 5:10pm UTC](https://discourse.haskell.org/t/h2jvm-a-haskell-library-for-writing-jvm-bytecode/14182 "2026-06-10T17:10:49Z")

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Hi everyone! I have been working on a new library for writing JVM bytecode with Haskell in a nice, high level way and I’d love some feedback on it! The motivation here is for compilers to the JVM so they can focus on th…

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