Issue 155 :: Haskell Weekly


Oops, I forgot to post this here last week!

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.


  • A cheatsheet to regexes in Haskell by William Yao

    While Haskell is great for writing parsers, sometimes the simplest solution is just to do some text munging with regular expressions.

  • Evaluating RIO by Patrick Brisbin

    As an experiment to see if we’d be interested in using rio in our applications at Freckle, I converted the main app in my Restyled side project to use it.

  • Every Day Recursion Schemes by David Smith

    In this post I want to present a simple pattern that I have started seeing quite often, I think it’s reasonably easy (and useful) to start using without really knowing what’s going on underneath.

  • Haskell coreutils - which by Austin

    On most operating systems (Linux, Windows, MacOS, *BSD), the PATH environment variable defines which directories contain executables. which helps you find an executable by searching through these directories.

  • – Haskell Web Development using Miso in Production by Daniel Smith

    Polimorphic’s codebase is written in Haskell. We have found Haskell to be a great pleasure to work with and thought it would be worthwhile to do a technical writeup for this sub.

  • Property-Based Testing in a Screencast Editor, Case Study 2: Video Scene Classification by Oskar Wickström

    This post covers the video classifier, how it was tested before, and the bugs I found when I wrote property tests for it.

  • Some limits of MTL with records of functions by Sam Halliday

    This is a follow up to address some of the shortcomings of the approach when a project scales, to explain why people continue to explore alternatives to MTL and why many Haskell developers do not consider application design to be a solved problem.

  • Stack: building GHC from source by Sylvain Henry

    With Stack 1.9.* we can’t use this kind of syntax to build GHC (and the other global packages such as base or template-haskell) from source. But as my patch has been merged, the next major release of Stack will support it!


  • Galois is hiring for a variety of roles (ad)

    Including but not limited to: Software Engineers/Researchers, Project Managers, Hardware Engineers, Red Team Lead, Software Integration Engineer.

    We collaborate with organizations like NASA, DARPA, and AWS to explore blue sky ideas and turn them into usable technology. Some of the things we’ve worked on in the past: Formal methods, static analysis, cryptographic algorithms, abstract interpretation, type theory, formal verification, reinforcement learning, autonomous systems assurance, communication security, cyber-deception for network defense, DDoS defense, provable hardware security, and statistical anomaly detection for detecting advanced persistent threats. We think working here is awesome; see

  • Haskell engineer at Obsidian Systems in Manhattan

In brief

Package of the week

This week’s package of the week is Propellor, a tool which ensures that the system it’s run in satisfies a list of properties, taking action as necessary when a property is not yet met.

Call for participation


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South America