Haskell Programming Language

Committed to a welcoming, vibrant & ﬂourishing #Haskell community!

Here we talk about community updates, software engineering and the joy of programming.

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Last Notes

2026-08-04 18:20:26 GMT

"A Revised #Haskell 2010 Language Report" by David Binder https://blog.haskell.org/revised-haskell-2010-report/

2026-07-10 10:15:34 GMT

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@nprofile…whz6 may we ask what it was?

2026-06-03 14:50:46 GMT

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@nprofile…ma3v And the time is now!

2026-06-02 21:34:21 GMT

The past years have seen horrendous attacks towards trans people. We have a duty to protect the most vulnerable members of our communities.
There is no #Haskell without the trans people who have shaped it through the years.
This June is a month of celebrations, but the struggle continues. ✊🏳️‍⚧️λ
https://cdn.fosstodon.org/media_attachments/files/116/682/655/965/174/186/original/5b54c3afc3be0295.png

2026-05-08 15:23:12 GMT

"Exception Annotations: Lay of the Land" by Edsko de Vries.
TL;DR: Use ghc 9.12, don’t call throwIO on an argument of type SomeException, and use your own function instead of displayException if you want to see all exception annotations.
https://well-typed.com/blog/2026/05/lay-annotation-land/
#Haskell

2026-05-03 17:33:39 GMT

A Tale of Two Handles and a Segfault – Adventures in tackling race conditions and flaky tests in HLS by Curtis Chin Jen Sem
https://crtschin.com/posts/a-tale-of-two-handles
#Haskell

2026-03-27 12:17:21 GMT

The Glorious Glasgow #Haskell Compiler version 9.12.4 is now available! This 4th patch release fixes critical codegen regression, crashes and brings improved backtrace supports.
See the release notes https://downloads.haskell.org/~ghc/9.12.4/docs/users_guide/9.12.4-notes.html

2026-03-22 12:27:46 GMT

Today is a great day for some major news!
DataFrame v1.0.0.0 has been officially released! Step up your exploratory data analysis in #Haskell with Typed data frames, direct connection to HuggingFace data sets, and Python integration through Apache Arrow.
https://discourse.haskell.org/t/ann-dataframe-1-0-0-0/13834

2026-03-04 14:19:44 GMT

Layoutz! Zero-dep Elm-style TUI’s for #Haskell - now w/ terminal plots & more
https://discourse.haskell.org/t/layoutz-0-3-2-zero-dep-elm-style-tui-s-for-haskell-now-w-terminal-plots-more/13760

2026-03-03 11:09:40 GMT

Notorious mad lad
@nprofile…5j98 has opened a GHC Proposal to add hints to guide branch prediction! https://github.com/ghc-proposals/ghc-proposals/pull/744
This may be key to better register allocation and code layout.
#Haskell

2026-03-03 10:52:23 GMT

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@nprofile…8xwg Congrats!

2026-03-02 20:09:59 GMT

It's there folks! The results of the State of #Haskell 2025 survey have been published
https://discourse.haskell.org/t/state-of-haskell-2025-results/13755

2026-03-02 13:22:17 GMT

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@nprofile…qrss Feel free to ask on the forum directly ;)

2026-02-27 20:04:27 GMT

Brillo 2.0 - Production ready 2D graphics
#Haskell #Graphics
https://discourse.haskell.org/t/brillo-2-0-production-ready-2d-graphics/13747
https://cdn.fosstodon.org/media_attachments/files/116/144/382/071/737/697/original/3b05c9d5e704f0d3.jpg

2026-02-24 13:55:57 GMT

New #Haskell Debugger Release: v0.12
https://discourse.haskell.org/t/new-haskell-debugger-release-v0-12/13732

2026-02-24 11:09:37 GMT

Sabela - A reactive Notebook for #Haskell by the #DataHaskell project
Announcement: https://discourse.haskell.org/t/ann-sabela-a-reactive-notebook-for-haskell/13728
Github Repository: https://github.com/DataHaskell/sabela

2026-02-22 18:53:19 GMT

Iced-hs, a #Haskell wrapper for the #Rust GUI library iced-rs, has been updated to iced 0.14.
Read more details at https://discourse.haskell.org/t/updated-iced-hs-to-iced-0-14/13715

2026-02-22 10:10:51 GMT

[ANN] kdl-hs 1.0.0 released with v2 support
kdl-hs is a parser for the #KDL configuration language, now compliant with the v2 standard.
https://discourse.haskell.org/t/ann-kdl-hs-1-0-0-released-with-v2-support/13712
#Haskell

2026-01-15 23:17:44 GMT

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@nprofile…cdfq have fun!

2026-01-15 22:45:46 GMT

Hyperbole 0.6, the #Haskell web framework for interactive applications with minimal JS, has been released! See it in action on https://hyperbole.live
Announcement: https://discourse.haskell.org/t/ann-hyperbole-0-6-viewstate-server-push-concurrency-controls-fancy-docs/13543

2026-01-13 08:41:42 GMT

State of DataHaskell Q1 2026
https://www.datahaskell.org/blog/2026/01/12/state-of-datahaskell-q1-2026.html
#Haskell #DataScience

2026-01-12 16:42:55 GMT

The #Haskell ecosystem survey closes in two days! Make your voice heard so that we know where to invest our resources: https://www.surveymonkey.com/r/6M3Z6NV

2026-01-09 21:39:30 GMT

"DataFrame January 2026 Updates"
https://discourse.haskell.org/t/dataframe-january-2026-updates/13512
#Haskell

2026-01-07 11:01:48 GMT

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@nprofile…8xwg Absolutely!

2026-01-07 10:44:47 GMT

#GSoC 2026 Call for Ideas
https://www.reddit.com/r/haskell/comments/1q5u3fk/gsoc_2026_call_for_ideas/
#Haskell

2026-01-07 10:42:07 GMT

"The Hazy Haskell Compiler" on Discourse
https://discourse.haskell.org/t/the-hazy-haskell-compiler/13497
#Haskell #Compiler

2025-12-31 12:13:26 GMT

Communication from the #Haskell Cryptography Group: "A vulnerability in #libsodium 's validation of ed25519 elliptic curve points: You are likely not affected"
https://haskell-cryptography.org/blog/libsodium-vulnerability-ed25519-valid-points/

2025-12-30 14:42:12 GMT

The best #Haskell pretty-printing library `prettyprinter` is looking for maintainers to help out! https://github.com/quchen/prettyprinter/issues/272

2025-12-26 18:11:07 GMT

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@nprofile…ehwj cabal has more people working on it these days. Stack's UX will not bring you a significant advantage from your perspective.

2025-12-26 17:48:59 GMT

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@nprofile…ehwj oh gitit *as packaged by debian*?

2025-12-26 17:11:55 GMT

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@nprofile…ehwj Good heavens what are you building?

2025-12-20 20:57:31 GMT

"Why does my favourite LLM have trouble with Haskell syntax?" is easily answered by the fact that constantly playing on probability (next token, three 7s on the coin slot) is gambling, and when you gamble, you have to be ready to lose.
https://fosstodon.org/@[email protected]/115752351285919767

2025-12-19 16:19:50 GMT

"Haskell ecosystem activities report: September–November 2025" by Well-Typed
https://www.well-typed.com/blog/2025/12/haskell-ecosystem-report-september-november-2025/
#Haskell

2025-12-18 21:40:06 GMT

MicroHs v0.15.0.0 release! 🎉
https://discourse.haskell.org/t/microhs-v0-15-0-0/13422
#Haskell

2025-12-18 21:39:12 GMT

"The Subtle Footgun of TVar (Map _ _)" by Matt Parsons
https://www.parsonsmatt.org/2025/12/17/the_subtle_footgun_of_tvar_(map____).html
#Haskell

2025-12-18 15:15:31 GMT

"A different way to do concurrency — #Haskell 's STM monad" by Elisabeth Stenholm
https://www.youtube.com/watch?v=d-NZnR2CTss

2025-12-14 17:02:50 GMT

🎉 Release 1.0.0 of ClickHaskell, the #Haskell implementation of ClickHouse DBMS Native protocol, has been published! See https://github.com/KovalevDima/ClickHaskell/releases/tag/v1.0.0 and https://clickhaskell.dev/

2025-12-14 16:58:01 GMT

"Easy Type-Level Flags In #Haskell" by Grégoire Locqueville
https://glocq.github.io/en/blog/20251214/

2025-12-11 03:49:25 GMT

Koreaboo #Haskell programmers should not forget to add GOCHUJANGLOG.md in the extra-doc-files section of their .cabal file.
https://cabal.readthedocs.io/en/stable/cabal-package-description-file.html#pkg-field-extra-doc-files

2025-12-10 20:14:51 GMT

The State of #Haskell 2025 survey is out! Please take ~10 minutes to fill this out and share it with friends/colleagues/coworkers, whether or not they are users of Haskell.
https://www.surveymonkey.com/r/6M3Z6NV

2025-12-06 19:24:32 GMT

Saint-Exupéry wrote “Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away.”
What would you like to see removed from #Haskell to help it achieve perfection?

2025-12-05 21:59:22 GMT

Layoutz – A tiny zero-dep lib for beautiful #Elm-style TUI's in #Haskell 🪶
https://flora.pm/packages/@hackage/layoutz
https://www.reddit.com/r/haskell/comments/1pe3qju/layoutz_020_a_tiny_zerodep_lib_for_beautiful/
https://discourse.haskell.org/t/layoutz-0-2-0-a-tiny-zero-dep-lib-for-beautiful-elm-style-tuis-in-haskell/13363

2025-12-02 18:08:06 GMT

This year, why not do the #AdventOfCode in #Haskell with your polycule?

2025-11-30 16:38:00 GMT

New post on the #Haskell blog: "Analyzing language extension semantics" from the Stability Working Group.
https://blog.haskell.org/investigating-language-extension-semantics/

2025-11-26 10:45:25 GMT

"Google Summer of Code 2025 Wrap-up" on the #Haskell blog! Come see what our students contributed to the ecosystem during their time! https://blog.haskell.org/gsoc-2025/

2025-11-26 09:19:07 GMT

"A tale of two kernels" on the DataHaskell blog https://www.datahaskell.org/blog/2025/11/25/a-tale-of-two-kernels.html
#Jupyter #Haskell

2025-11-21 13:48:24 GMT

Did you know? While not a perfect replacement, `cabal` can use Stackage package sets by importing the version constraints file that is provided by stackage.org. Create a `cabal.project` file and add the lines:
```
packages: ./
import: https://www.stackage.org/lts-24.4/cabal.config
```
🥳
#Haskell

2025-11-13 13:46:44 GMT

Awesome!
https://functional.cafe/@hungryjoe/115542308604198218

2025-11-12 15:30:38 GMT

"Composing Event Migrations with Default Implementations" from the Hindsight blog https://hindsight.events/content/posts/composing-event-migrations-with-default-implementations.html
#Haskell #EventSourcing

2025-11-11 22:44:56 GMT

Welcome to dataHaskell (revived)! https://www.datahaskell.org/blog/2025/11/11/welcome-to-datahaskell.html
by @nprofile…hsu4
#Haskell #DataScience

2025-11-11 14:38:21 GMT

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@nprofile…f9ft :3

2025-11-11 12:57:07 GMT

It's with great pleasure that we are announcing that @nprofile…f9ft is sponsoring the #Haskell project, by providing high-performance CI infrastructure for the Glasgow Haskell Compiler! Thank you!

2025-11-06 08:37:07 GMT

"Patterns and Paradoxes: The Logic of Pattern Synonyms" by @nprofile…rk8s https://www.mlabs.city/blog/patterns-and-paradoxes
#Haskell

2025-11-06 08:34:36 GMT

"Cheaper: producing a program with less developer time" by Alexandre Esteves: https://github.com/alexfmpe/semantic-satiation/blob/main/src/Posts/002-cheaper.md
#Haskell

2025-11-01 14:49:00 GMT

"Case Study: Debugging a Haskell space leak" by Matthew Pickering from Well-Typed https://www.well-typed.com/blog/2025/10/case-study-debugging-space-leak/
#Haskell

2025-10-29 11:35:49 GMT

Announcing Hindsight, an event sourcing library for #Haskell, designed to bring type safety and correctness to event-driven architectures.
https://hindsight.events/content/posts/announcing-hindsight.html

2025-10-27 17:59:03 GMT

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@nprofile…huu7 To advance the state of the art

2025-10-25 19:29:21 GMT

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Congratulations to @nprofile…wlcv for the work!

2025-10-25 19:28:41 GMT

This is not a drill: GHC (the #Haskell compiler) now runs in your browser. See the announcement (and please report any bugs) here: https://discourse.haskell.org/t/ghc-now-runs-in-your-browser/13169

2025-10-23 08:26:30 GMT

Call for Servant cookbooks in preparation of v0.21
https://discourse.haskell.org/t/call-for-servant-cookbooks-in-preparation-of-v0-21/13162
#Haskell #Documentation

2025-10-09 11:06:19 GMT

Programming languages of the ML family are often heralded as having powerful type systems that allow them to model the complexity of the real world, in a way that is less bad than the competition. The potential absence of a value is described not an implementation detail due to an undefined/null…

2025-10-08 21:59:14 GMT

The mad lads have made it: Two Haskellers went to the town of #Haskell, TX. They documented their journey here: https://www.youtube.com/watch?v=9KwWGulBtyA
See on Reddit: https://www.reddit.com/r/haskell/comments/1o1202q/cowboys_from_haskell/

2025-07-21 20:57:57 GMT

Long before vibe coding platforms deleted your production databases, GHC deleted your code if it failed to typecheck.
The ultimate production incident awaiting its ultimate practitioner.

2025-06-17 11:41:23 GMT

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And since these are all Haskell types (once parsed from the outside) you can have well-typed transformations between them. It's so silly how OP this technique is, despite being low-tech.

2025-06-17 11:41:14 GMT

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Sometimes you may, by chance, bundle some of these types together but it is only temporary. And reality will catch up with you once you've broken your JSON consumers by changing the representation of an entity in your code.

2025-06-17 11:41:03 GMT

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Between these two, your Business (or Domain) Objects can be as expressive and powerful as you want, because ultimately they are the ones who encode the business rules, the state transitions, the invariants.
Want to use TypeData/DataKinds? Go off! This is where you handle the complexity of the domain

2025-06-17 11:40:44 GMT

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The Data Access Object (DAO) is the data type that will be serialised for storage into your database. No fancy nesting (unless you're storing JSON), and similarly, backward compatibility measures must be implemented when parsing data back from the DB.

2025-06-17 11:40:32 GMT

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The Data Transfer Object (DTO) encodes the constraints of how you emit data out of your system. Ideally, you automagically derive a record into this format, like with https://flora.pm/packages/@hackage/deriving-aeson
Since it is meant to be consumed by clients you want to version it, or at least maintain backward compatibility.

2025-06-17 11:40:06 GMT

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You may be able to to store JSON directly into your SQL database, but does that mean that it is the most expressive and powerful way of modelling your business domain? No.
This means that in practice, whether you want it or not, you have three types of objects that represent each case[…]

2025-06-17 11:39:49 GMT

Sorry to those who need to hear it, but lambda is not the ultimate software architecture model. You think you have a "simple" web application that speaks to a database and emits JSON. Wrong!
You have a system that needs to speak two different languages, whose grammar and constraints and different…

2025-06-17 08:18:14 GMT

Sometimes you think you're a silly little open-source maintainer, and one day you receive an email from NASA about supplier assessment.

2025-06-16 11:05:10 GMT

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https://fosstodon.org/@haskell/114692651945929418

2025-06-16 11:05:07 GMT

Picking up #Haskell is not a matter of "If" but of "When".
When your head overflows with UML diagrams instead of expressive yet concise types?
When your systems belch runtime exceptions like a Weezing?
When shared mutable state prevents you from understanding what the hell is happening?

2025-06-16 10:49:43 GMT

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“Undefined method for nil:NILClass” We do not have to live like this.

2025-06-16 10:49:31 GMT

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There is a world of cool testing methods out there to be discovered! Don't think tests are a burden, because tests are the custodians of your code base. Every behaviour you clarify and result you expect saves you from being paged at 3:00 in the morning on a week-end.

2025-06-16 10:49:29 GMT

Some people hear “ #Haskell 's type system eliminates entire classes of bugs” and think “Cool, no tests needed”.
But what you should hear is “Cool, we can focus on more interesting tests”.
Golden tests, property tests, doctests…
https://wiki.haskell.org/index.php?title=How_to_write_a_Haskell_program#Testing

2025-06-16 10:35:41 GMT

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Check this evergreen keynote by @nprofile…57a0 https://www.youtube.com/watch?v=A9vRp9T8pkU

2025-06-16 10:34:58 GMT

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Or worse, between CLI tools that need to be release in a synchronous fashion, yet in practice are maintained by independent teams. Build System, Compiler & Language Server suffer from this.
So, congratulations, you have a distributed monolith: https://mehmetozkaya.medium.com/microservices-antipattern-the-distributed-monolith-%EF%B8%8F-46d12281b3c2

2025-06-16 10:34:41 GMT

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Now, if you know what you are looking for when addressing coupling issues, you will see that simply "splitting apart" a monolith into services may only address *some* issues (like velocity of development), but will also maintain coupling between these new services, now over the network.

2025-06-16 10:34:19 GMT

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Without surprise, "loosely coupled components" survive the test of time much better than a monolithic architecture. Think of React versus The Elm Architecture, for instance. TEA is awesome to get a good idea of what you initially need for your data model. […]

2025-06-16 10:34:11 GMT

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Simultaneously, decoupling incurs a real cost. So there's a balance to be stricken, in order to maintain an architecture that enables low-cost change, while enabling engineers to work on said changes instead of recursively decoupling the whole software stack until we reach the silicon atoms.

2025-06-16 10:34:02 GMT

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As such, the cost of software is proportional to the coupling in your architecture.
This is especially true when software leaves the "quick prototyping for reaching MVP" phase. Because empirically, most new features are built on old features & foundations.

2025-06-16 10:33:53 GMT

In software engineering, the cost of software is the cost of change, and not all change cost the same. At some point, your architectural model stops accommodating "cheap" changes, and forces you to change more things than expected. And we call this "coupling"
[…]

2025-06-16 10:33:27 GMT

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@nprofile…dhw9 Nope, rail travel has to happen in soft real-time ;)

2025-06-06 15:17:29 GMT

🚨 BREAKING NEWS 🚨
Railway in Europe deemed “critical infrastructure” as the amount of #Haskell users heading to Switzerland exceeds usual average, due to #ZuriHac.

2025-06-03 09:13:43 GMT

In this Pride Month, let us remember that #FunctionalProgramming has the privilege and honour to share our beloved λ with the Lesbian community. Let's go Lesbians!
https://cdn.fosstodon.org/media_attachments/files/114/618/662/473/818/560/original/a18bbb548c5f4c98.png

2025-04-15 19:06:45 GMT

#Haskell Language Server 2.10.0.0 release announcement!
blog.haskell.org/hls-2-10-0-0/
#LSP #FunctionalProgramming

2025-03-24 08:33:13 GMT

GHC 9.6.7 is now available!
https://discourse.haskell.org/t/ghc-9-6-7-is-now-available/11697
#Haskell
https://cdn.fosstodon.org/media_attachments/files/114/216/479/427/936/891/original/9e8eebb45b5cac98.png

2025-02-24 14:20:46 GMT

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Update n°42 from the GHC team at IOG
https://engineering.iog.io/2025-02-20-ghc-update
Highlights:
• Sylvain worked on making GHC built with cabal-install pass the testsuite
• Luite looked into using cosmopolitan libc to see if we can make a GHC cross compiler that produces multi-arch/os binaries
#Haskell

2025-02-24 14:18:33 GMT

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Update n°41 from the GHC team at IOG
https://engineering.iog.io/2025-01-30-ghc-update/
Highlights:
• Luite has completed the GHC 9.6.7 release.
• Sylvain worked on bootstrapping GHC and boot libraries with cabal-install
#Haskell

2025-02-22 13:08:28 GMT

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A monkey's paw somewhere just had one finger curl.

2025-02-22 13:06:53 GMT

This past week in the #Haskell Security Advisories:
*checks notes*
Nothing. Business as usual it is then.

2025-02-22 12:36:30 GMT

The GHC developers are very pleased to announce the availability of the second release candidate of GHC 9.6.7
Release notes: https://downloads.haskell.org/ghc/9.6.7-rc2/docs/users_guide/9.6.7-notes.html
Announcement: https://mail.haskell.org/pipermail/ghc-devs/2025-February/021939.html
#Haskell #FunctionalProgramming

2025-02-01 10:21:26 GMT

Registrations for #ZuriHac are open!
https://fosstodon.org/@zurihac/113923721436690162
#Haskell #FunctionalProgramming

2025-01-09 13:19:17 GMT

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Update n°40 from the GHC team at IOG
https://engineering.iog.io/2025-01-09-ghc-update/
Highlights:
• Luite finalized the patch adding compiler flags to to switch off speculative evaluation.
• Sylvain worked on bootstrapping GHC with Cabal.
#haskell

2025-01-09 09:15:17 GMT

New post on the #Haskell blog: “Case Study — Using a JavaScript component inside a Haskell application”
https://blog.haskell.org/case-study-foreign-integration-js-browser/

2025-01-06 11:03:59 GMT

GHC 9.12 & Cabal 3.14 released!
Read the announcement at https://blog.haskell.org/ghc-9-12-cabal-3-14/
#Haskell
https://cdn.fosstodon.org/media_attachments/files/113/781/075/096/007/247/original/ef117f38f8037d8b.png

2024-12-23 11:20:20 GMT

The Cabal Manual now has a guide on how to collect performance statistics of Haskell applications. Read more at
https://blog.haskell.org/how-to-collect-performance-statistics-with-cabal/
#Haskell #Profiling

2024-12-23 11:07:57 GMT

#Haskell Interlude's guest Tom Ellis works at Groq, using Haskell to compile AI models to specialized hardware. Listen to this episode about stability of both GHC and Haskell libraries, effects, and strictness.
https://haskell.foundation/podcast/60/

2024-12-23 10:59:10 GMT

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Update n°39 from the GHC team at IOG
https://engineering.iog.io/2024-12-19-ghc-update/
Highlights:
• Sylvain kept working on building GHC with cabal-install instead of Hadrian
• Jeff: created a GHC JS Backend matrix room come chat about all things JS backend!
• Luite Is back from vacation and has been preparing the GHC 9.6.7 release. Welcome back Luite!
#haskell