Haskell Weekly


Issue 180 2019-10-10

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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.


  • Verifying the Titular Properties of a Leftist Heap by Mistral Contrastin

    In which my job search leads me to verify the leftist and heap properties of a leftist heap using Haskell’s type-level features and to test various implementations by way of simulation using QuickCheck.

  • Bazel, Cabal, Stack: Why choose when you can have them all? by Mathieu Boespflug & Andreas Herrmann

    Users frequently ask which build tool to use for their next project. It turns out that “all of them at once” is a compelling answer (including Nix, though we covered that previously and won’t be rehearsing that in this post).

  • You are already smart enough to write Haskell by William Yao

    Picking up any other language seems like a straightforward endeavor; read a few tutorials, try to write a project that interests you, and you’re off. Why is Haskell so much more intimidating?

  • A new book about programming with Haskell by John Whitington

    Haskell from the Very Beginning will appeal both to new programmers, and to experienced programmers eager to explore functional languages such as Haskell.

  • Good design and type safety in Yahtzee by Tom Ellis

    We can’t just expect to sprinkle type safety on a bad design and get something good. Type safety and good design are qualities that evolve symbiotically.

  • Nicer Data Types a la Carte with DefaultSignatures by Yair Chuchem

    Back in 2008, Swierstra’s Functional Pearl Data Types a la Carte showed how to construct the following data structure: data Expr = Val Int | Add Expr Expr, from simple and re-usable individual components


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

In brief

  • speedscope by Jamie Wong

    Welcome to speedscope, an interactive flamegraph visualizer. Use it to help you make your software faster.

  • Episode 21: Event Log by Haskell Weekly Podcast

    Cody Goodman and Taylor Fausak explore the event log that GHC can produce when compiling or running.

  • Why we decided to go for the Big Rewrite by Robert Kreuzer

    In this post we will try to give a more general framework on how to answer this question for a specific project and we will also tell our story of rewriting the core data processing system that powers Channable.

Package of the week

This week’s package of the week is bitvec, a library that provides a newtype over Bool with a better Vector instance: 8x less memory, up to 1000x faster.

Call for participation

Looking for something to work on? Browse Haskell Hacktoberfest issues on GitHub.