Haskell Weekly


Issue 266 2021-06-03

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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.


  • Declaration groups: where order of declarations suddenly matters in Haskell by Artyom Kazak

    Let’s say you have a few types that reference each other. Now you want to generate lenses. And suddenly you are hit with this seemingly unrelated error. What gives?

  • Final tagless encodings have little to do with typeclasses by Ben Levy

    I would like to argue that what people are referring to as final tagless is in fact just coding against an interface and that the novelty of final tagless really has very little to do with abstract interfaces.

  • Getting started with Haskell projects using Scotty by Juan Pedro Villa Isaza

    As part of our internal Haskell training, we use a URL shortener as a way to get started with Haskell projects and web applications in particular.

  • Phantom Types and Globbing Bugs by Patrick Brisbin

    I love concrete examples that illustrate the day-to-day of the professional Haskell programmer, and show the inspiration for that entirely-untrue quip, “if it compiles, it works”.

  • Simple Haskell Handbook with Marco Sampellegrini by Haskell Weekly Podcast

    Special guest Marco Sampellegrini talks with us about his recent book, The Simple Haskell Handbook. The book describes a project driven approach to Haskell development, using a continuous integration server as a motivating example.

  • Stack on Slack and ARM64 by Michael Snoyman

    This blog post is covering two completely unrelated announcements about Stack that happened to land at the same time.

  • Stackage nightly snapshots to switch to GHC 9.0.1 by Chris Dornan

    We have been looking for an opportunity to switch to GHC-9 on our nightly builds and have decided that GHC-9 has been out long enough and we need to get on with preparing the ecosystem for its eventual deployment as the Haskell toolchain of choice.

  • a stacker does cabal by Tony Day

    I type this having deleted ./.stack. All stack.yamls have been erased, which stack points to null. Onward we march to cabal or bust!

  • The Voids Of Haskell by Alexander Granin

    When it comes to the closer comparison with any other mainstream language, we see that not everything in the Haskell ecosystem is good enough.

  • Why do I think Haskell is a good choice in regards to Software Security? by Ville Tirronen

    The Typeable Team appreciates security! We love Haskell, but is Haskell a good choice when secure software is the goal?


  • Haskell @ Mercury

    Mercury is building a bank for startups. We’re hiring Haskell engineers (generalist and backend). Apply if you want to work with Haskell/Yesod/Persistent and React/Redux/Typescript. You can check out <www.lifeatmercury.com> (pw: charlietuna). Reach out to veronica@mercury.com with questions.

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

In brief

Show & tell

  • safe-wild-cards by Artyom Kazak

    I have just released a small library, safe-wild-cards, that lets us have safer wildcard matches at the cost of somewhat worse syntax.

  • tophat by James Cranch

    Template-to-Haskell preprocessor and templating language

Call for participation