Haskell Weekly


Issue 311 2022-04-14

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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 activities report: February–March 2022 by Well-Typed

    This is the eleventh edition of our GHC activities report, which describes the work on GHC and related projects that we are doing at Well-Typed. The current edition covers roughly the months of February and March 2022.

  • An Interface for accessing Environment Variables by Felix Springer

    For me dependent types are the most natural way to semantically reason about programs. Unfortunately dependently typed languages are not really production-ready yet. Haskell and GHC often come close enough.

  • It Doesn’t Have to Be Arbitrary by Michael Gilliland

    At Freckle, we have a large Haskell codebase that’s rigorously tested using randomized data and property-based testing. After years of defining Arbitrary instances we’ve come up with the following guidelines to keep test overhead low and maximize the benefits of property-based tests.

  • Two for One: Using concatMap by Monday Morning Haskell

    Today’s for-loop replacement is a simpler one that combines two functions we should already know! We’ll see how we can use concatMap to cover some of the basic loop cases we might encounter in other languages.

  • What’s That Typeclass: Monoid by Gints Dreimanis

    In programming, there’s a pattern that occurs very frequently — putting together two things of the same type to get another thing of that type. Given its frequency, it would be nice to have some useful abstractions for it.


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Show & tell

  • Copilot version 3.8 and Ogma version 1.0.2 by Ivan Perez

    A few weeks ago we put out Copilot 3.8. Copilot is a Runtime Verification framework that compiles to hard real-time C99. The effort at present is on stability, cleaning, and providing further assurances with the code generated.

  • idiomatic by Baldur Blöndal

    Idiomatically is used with DerivingVia to derive Applicative for types with multiple constructors.

  • linear-builder by Andrew Lelechenko

    Linear types for linear times! Builder for strict Text, based on linear types.

  • Simulated Annealing by Mathias Jean Johansen

    As the algorithm runs, it stores each step of the optimization process in a tour history, and once the algorithm has finished execution, it will animate these steps using SDL2.

Call for participation