Haskell Weekly

Welcome to another issue of Haskell Weekly! Haskell is a safe, purely functional programming language with a fast, concurrent runtime. This is a weekly summary of what’s going on in its community.

Featured

• Haskell ecosystem activities report: March–May 2026 by Well-Typed

  This is the thirty-first edition of our Haskell ecosystem activities report, which describes the work Well-Typed are doing on GHC, Cabal, HLS and other parts of the core Haskell toolchain. The current edition covers roughly the months of March 2026 to May 2026.

• Nix for Haskell: Static Builds by Abhinav Sarkar

  In the previous post, we learned how to get started with managing and building a Haskell project with Nix. In this post, we learn how to easily create statically-linked executables for Haskell projects with Nix.

• pqi: Making libpq a Choice, Not a Requirement by Nikita Volkov

  For years, every serious Haskell PostgreSQL driver has been chained to the same C library - libpq - with no clean way out. I tried to cut it loose twice, and both times I failed at the finish line. They say the third time’s the charm. I hope it will be - not because I’ve tried harder, but because I’ve changed the goal.

• Record type inference for dummies by Gabriella Gonzalez

  The reason I’m writing this post is because I actually wanted to write a more advanced post on type inference for anonymous records, but then I realized that most of my readers wouldn’t understand the latter post in isolation. So I figured I would write this introductory post to teach people new to type theory the basics.

• Sheaves in Haskell by Arnaud Spiwack

  I recently found a way to represent sheaves in Haskell. It was a fun couple of weeks of head-scratching. But as much as I wanted it to, the code in my demonstration repo doesn’t speak for itself. So I’m writing this blog post to share my newfound understanding. In this post I’ll be assuming a pretty solid knowledge of category theory (but not of sheaves, which I’ll be explaining). If you aren’t, wait until my next post which will give a more practical introduction to sheaves.

In brief

• A wild apecs-0.10.0 appears! by wiz

  After 2.5 years of using it from git master, I’m now finally committed enough to publish an update for the venerable ECS package.

• Fourmolu 0.20.0.0 released by Brandon Chinn

  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!

• GHC 9.12.5-rc2 is now available by MangoIV

  The GHC developers are very pleased to announce the availability of the second release candidate for GHC 9.12.5, ghc-9.12.5-rc2.

• Hpack-Dhall with Cabal commands by Phil de Joux

  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.

• Stock: Stock-style deriving via coercion, with no Generic by Iceland_jack

  A package for extensible compile-time deriving.

Show & tell

• A Quick Tour of a (WIP) Pure Haskell Software Renderer by Tobi

  This is a pure Haskell CPU renderer I’ve been working on in my free time since I started it in March 2026. It is currently tiled-deferred, but I would also like to build in the capability to forward render with it so transparencies can be added in a separate pass. A lot of work will go into making it faster; ideally, I want to see how fast it can get using only pure Haskell.

Call for participation

• RFC “http-types” breakage / additions / rework by Felix Paulusma

  I am requesting comments from everyone who has experience in web development, networking and/or has strong opinions about library stability/documentation/improvement.

• 2.5 hour Haskell Foundation Online Workshop by José Manuel Calderón Trilla

  Please join us this Friday for 5 talks on the uses of AI in Haskell development.

• ghc-stack-profiler: Emit version message on eventlog startup