Haskell Weekly


Issue 289 2021-11-11

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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.


  • 2021 State of Haskell Survey by Haskell Weekly

    This survey opens on November 1st and closes on the 15th. The goal of this survey is to better understand what people think of the Haskell programming language, together with its ecosystem and community.


  • Haskell eXchange Online Conference (November 15–17, 2021) (ad)

    Join us as we explore the latest Haskell tools and libraries with 25 talks by Haskellers from around the globe. PLUS — we’ve got a FREE day of beginner-friendly sessions for anyone new to the language. Ticket includes exclusive access to recordings. Haskell Weekly subscribers enjoy 15% off code HW15.

  • How To Use a Record Field Name Within a Haskell Module Twice by Malte Neuss

    We take a beginner-friendly, detailed look at what you can and cannot do with the DuplicateRecordFields extension without resorting to field labels or lens libraries.

  • An Epic future for SPJ by Simon Peyton Jones

    As you may know, I am leaving Microsoft Research at the end of November. Time for something new! I am going to start a new role as Engineering Fellow at Epic Games in December.

  • Graphula by Patrick Brisbin

    Its responsibility is to define and insert arbitrary values and their relations into the database ahead of running a test, while giving you control to tailor the data for that test’s needs, and to keep it all succinct and readable.

  • Haskell in Production: Scarf by Gints Dreimanis

    In this edition of our Haskell in Production series, I interview Avi Press, the CEO & co-founder of Scarf. In the interview, we talk about where Scarf uses Haskell in their projects and what have been the benefits and downsides of the language choice.

  • A Haskell memory leak in way too much detail with Cachegrind by Jeffrey Young

    So, if you’re interested in low-level optimization of your Haskell programs then this article is for you. I’ll demonstrate the use of a valgrind tool, cachegrind, to inspect the behavior of the canonical leaky Haskell program: a lazy left fold.

  • Simple, type-safe string formatting in Haskell by Dan Soucy

    Years ago, on a distant website, Lennart Augustsson responded to a question about how printf can work in Haskell, and whether it is type-safe: You can only get a type safe printf using dependent types.

  • A Static Haskell/Reflex Frontend App by Jack Kelly

    Over the past couple of days, I built my first static frontend application using reflex. It’s called CASAAAAA (try it out), and it’s an interactive fuzzy searcher for aviation terms.


  • Software Engineer at ACI Learning

    We are currently accepting applications for full-stack software professionals to join our small, but talented, multidisciplinary team.

  • Channable is looking for a Haskell team lead (ad)

    Channable is always hiring talented Haskell engineers and is now looking for someone to lead one of our Haskell teams. We’re a fast-growing international scale-up and while you can still benefit from the start-up vibe, working at Channable also means being part of a professional company with an outstanding development team.

  • Haskell Developer at MLabs (ad)

    We are one of the leading Haskell consultancies in the fintech, blockchain and AI space, with a passion for Haskell and open source software. We are looking for a remote Haskeller to join our team. If you are excited about Haskell and are up for a new challenge, please apply here or visit our website! For any questions please email mark@mlabs.city.

Trying to hire a Haskell developer? You should advertise with us!

In brief

  • GHC 9.2.1 by Haskell Weekly Podcast

    We’re back! After a month off, Cameron and Taylor get together to talk about what’s new in the Haskell world.

Show & tell

  • Autodocodec by Tom Sydney Kerckhove

    Get correct-by-construction JSON encoding, decoding, and documentation of your type using a single instance!

  • Copilot version 3.6 by Ivan Perez

    We are pleased to announce the release of Copilot 3.6, a stream-based DSL for writing and monitoring embedded C programs, with an emphasis on correctness and hard realtime requirements.

  • IHP version 0.16 by Marc Scholten

    A new IHP release with new features and many bug fixes. IHP is a modern batteries-included haskell web framework, built on top of Haskell and Nix.

  • Tangle by Fumiaki Kinoshita

    This package implements an abstraction of record construction where each field may depend on other fields.

Call for participation