Haskell Weekly


Issue 258 2021-04-08

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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.


  • GHC 9.2.1-alpha1 now available by Ben Gamari

    The GHC developers are very happy to announce the availability of the first alpha release in the 9.2.1 series.

  • Too Much Power Will Kill You (Every Time) by Marko Dimjašević

    Today there is a bug, and you won’t understand why, you’d give your life, you’d sell your soul, but here it comes again, too much power will kill you every time.

  • Category Theory Illustrated: Orders by Boris Marinov

    As mathematicians we are not interested in the criteria that we can use to order objects, but in the nature of the relationship that defines the order.

  • Custom Type Errors for Unordered Function Application by Michael Sloan

    In the previous post, a combination of a typeclass, closed type family, and associated type family was used to define an operator, (?). This operator provides type-directed function application, where the argument is provided to the first parameter that has a matching type.

  • Default exception handler in Haskell by Taylor Fausak

    This post will explain why you might want a default exception handler, how to install one, and point out a tricky edge case to watch out for.

  • Why kind-level foralls don’t interact with ScopedTypeVariables by Ryan Scott

    In this post, I will explain this discrepancy between kind-level foralls and other forms of forall. As it turns out, a key part of the story is that certain type-level declarations, such as type synonyms and type families, have arities.

  • Z.Haskell project announced by Dong Han

    After having a discussion with HF guys, I decide to announce Z.Haskell project, It’s available on Hackage and very much usable now, the document is also pretty adequate.


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

In brief

  • The Benefits of Learning Haskell by Alistair Burrowes

    My belief is that in terms of long term improvement, learning Haskell is one of the best ways to up your raw programming ability.

  • Capturing Number Theory in Haskell by Boro Sitnikovski

    In Chapter VII of GEB, the author gives a description of Gentzen’s Propositional Calculus, along with some examples of applying its rules, and in Chapter VIII, the author gives a description of TNT (Typographical Number Theory).

  • Compucolor II: A 1977 Home Computer recreated in Clash by Gergő Érdi

    This is a Clash implementation of the 1977 Compucolor II home computer manifactured by the CompuColor Corporation until 1980.

  • Giml’s type inference engine by Gil Mizrahi

    Giml’s type inference engine uses unification-based constraint solving.

  • Monthly Hask Anything (April 2021)

    This is your opportunity to ask any questions you feel don’t deserve their own threads, no matter how small or simple they might be!

  • Splitting function definitions across modules by Jaro Reinders

    Have you ever been annoyed that you have to define your functions all at once? Me neither, but nevertheless, I have been thinking about a way of solving this issue with Template Haskell.

Show & tell

  • alpaca-netcode by David Eichmann

    A rollback/replay client-server system for realtime multiplayer games. The API only requires you to express your game as a pure, deterministic function.

Call for participation