Haskell Weekly


Issue 177 2019-09-19

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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.


  • Tripping up type inference by Csongor Kiss

    Type inference is a blessing, but sometimes it can also be a curse. Inference too good can hinder the readability of code, because the compiler knows what the type of an identifier is even when we don’t.

  • Type-safe JSON queries for Esqueleto by Phil Freeman

    Wouldn’t it be nice if we could use the type information we already have to verify that we only use these operators correctly, and remove the unnecessary Maybes?

  • Building Lenses by Mitchell Vitez

    Implementing basic Haskell lenses in twenty exercises.

  • A cheatsheet to the time library by William Yao

    The de-facto standard date and time library in Haskell, time, however, can be a little obtuse to get started with. I always feel like I have to reread the documentation every time I need to write date-related code.

  • These Changes by Fintan Halpenny

    What we’ll cover in this post is what the These data type is, how it can be used, and how we used it to manage feature flags & safe code migrations.

  • The lenses book: Optics By Example - Early Access by Chris Penner

    I’m super excited to announce that I launched Early Access for Optics by Example today! This aims to be a comprehensive book on getting stuff done with optics taking folks through from beginners to advanced levels.

  • Interesting Music in Four Lines of Code by Donya Quick

    One of the strengths of the Euterpea library is the ability to generate complex musical values extremely concisely. Here I’m going to walk through an example of that, the results of which I then took and turned into a more serious composition.

  • Haskell compilation pipeline and STG language by J Ho

    We think that having Haskell compile to .Net with easy seamless interoperability with existing .Net libraries would significantly boost Haskell’s popularity with “mainstream” developers and help with wider industry adoption.

  • Why I prefer functional programming by Mario Morgenthum

    How could it happen that an imperative style developer converts into a Haskell fan? In this article I want to explain it– especially for developers with less experience in functional programming.

  • What is datatype-generic programming? by Max Hallinan

    This is an attempt to explain datatype-generic programming or “generics” in terms of the big picture, addressing my own points of confusion.


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In brief

Package of the week

This week’s package of the week is generic-constraints, a library that allows you to write standalone deriving without boiler-plate.

Call for participation