Haskell Weekly


Issue 172 2019-08-15

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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.


  • Practical Profunctor Lenses & Optics In PureScript by Thomas Honeyman

    Armed with a handful of types and functions, you can manipulate even complex data structures with minimal effort.

  • Inventing Monads by Kabir Shah

    It might sound a little crazy at first, but imagine being able to override the semicolon to reduce boilerplate in specific code blocks.

  • Rounding by Type Classes

    In contrast to previous installments of the featured function series, this article will cover four functions with identical types, from the same typeclass, that do not do the same thing.

  • Shorter GC pauses coming to GHC by Pepe Iborra

    GHC 8.10 is getting a new incremental garbage collector with a mark & sweep strategy for the older generation collections, as an alternative to the standard copy collector.

  • Vim and Haskell in 2019 by Marco Lopes

    I was pleasantly surprised to find out that things seem to have evolved quite a bit since then, and that Haskell in vim is now pretty feature rich.

  • Easy IHaskell Docker Images with Nix by Vaibhav Sagar

    I hope this is useful as a way of making IHaskell even more widely available, and as a demonstration of using dockerTools to bridge the gap between Nix and Docker!

  • Announcing pretty-simple- by Dennis Gosnell

    This post gives a short introduction to pretty-simple, explains the new features, and lists some outstanding issues I’d like help with.

  • ANN: cabal-fmt by Oleg Grenrus

    I have been using cabal-fmt for over a half year now for my own Haskell projects, and have been happy with this minimal, yet useful tool.

  • Who Authorized These Ghosts!? by Ollie Charles

    While playing around with ideas, I was reminded of the wonderful paper “Ghosts of Departed Proofs”, and it got me thinking… can we use these techniques for authorization?

  • Overriding Type Class Instances by Cary Robbins

    When you have an instance in scope, you are stuck with it. Is this a feature? Is this a bug?


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

In brief

Packages of the week

Many packages have been announced or received significant updates recently. We couldn’t pick just one to feature. Enjoy!

Call for participation


Meetup will change their API soon. As a result we decided to stop maintaining this section. Please see this issue for details: https://github.com/haskellweekly/haskellweekly.github.io/issues/272.