Haskell Weekly


Issue 219 2020-07-09

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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.


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  • A fork of Haskell prometheus-client by Alexander Vershilov

    For the last few months, I slowly work on improving the prometheus-client library. And I’d like to share some details of that work.

  • Automatic UI’s for Command Lines with cmdargs by Neil Mitchell

    I always thought it would be a neat trick to transform that into a web page, to make it easier to explore command line options interactively.

  • Beautiful Mutable Values by Justin Le

    Take back the power of mutable objects with all the safety and explicit state of Haskell.

  • Composing predicates by Christian Gill

    A few days ago I was writing some validation functions that were basically a composition of several other predicates.

  • How I integrate ghcid with vim/neovim by Roman Cheplyaka

    All we need is a few tweaks to make them play well together. This article describes the setup, which I’ve been happily using for 1.5 years now.

  • Introducing hasql-queue by Jonathan Fischoff

    I’ve recently released hasql-queue, a PostgreSQL backed queue for the hasql ecosystem.

  • Modeling state machines with dependent types in Haskell: Part 1 by Evgeny Poberezkin

    Modeling state transition in types offers a simple alternative to ensure that only allowed state transitions can be implemented - the code that attempts to perform the state transition that is not allowed will not compile.

  • Retrie: Haskell refactoring made easy by Facebook Engineering

    We’ve open-sourced Retrie, a code refactoring tool for Haskell that makes codemodding faster, easier, and safer.


  • Software Engineer at ITProTV

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  • Interos is Hiring Full Stack Haskell Software Engineers (ad)

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Upcoming events

In brief

  • Back to old tricks .. (or, baby steps in Rust) by Don Stewart

    As a warm up I thought I’d try porting the stream fusion core from Haskell to Rust.

  • Haskell/Python/Go web scraper comparison completed by Ryan Westlund

    The Python HTML library I used was higher-level than the Haskell and Go ones, and commenters pointed out alternatives that would significantly improve Haskell and Go.

  • My first foray into Rust by Sam Tay

    A story of coming to Rust from Haskell.

  • Some thoughts on building software by Alejandro Serrano

    This has brought some thought from the background of my brain about how we should model, organize, and architect software using the lessons we’ve learnt from functional programming.

  • Summer Course Sale! by Monday Morning Haskell

    As a special bonus, for this week only, both of our courses are on sale, $100 off their normal prices!

  • Surprise discount by A Type Of Programming

    A Type of Programming for just £25! 180.000 words in over 800 pages.

Show & tell

  • Hode by Jeffrey Benjamin Brown

    Hode is, loosely speaking, a hypergraph editor.

  • knit-haskell by Adam Conner-Sax

    In essence, knit-haskell is a (polysemy) stack of helpful effects atop Pandoc.

Call for participation