Haskell Weekly


Issue 325 2022-07-21

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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.


  • Configuration of a Polysemy application by Thomas Mahler

    One question that came up: why did I explicitly load configuration before starting the Polysemy effect interpreter? Wouldn’t it be much more in line with the overall idea of my Polysemy Clean Architecture to handle this loading also as an effect?

  • The Lazy Way to Solve Differential Equations by Iago Leal de Freitas

    By the end of this post we gonna be able to solve this differential equation simply by writing the equivalent Haskell definition

  • One of a Kind: An Introduction to Kinds in Haskell

    Just as Haskell has a type system to classify values, it has a kind system to classify types. It provides a way to reason about what types make sense to construct.

  • Parallelising Source Positions by Benjamin Hodgson

    My parsing library Pidgin has some infrastructure to track positions in a textual input file, for the purposes of error reporting.

  • Universal and Existential Quantification in Haskell by Stepan Prudnikov

    In logic, there are two common quantifiers: the universal quantifier and the existential quantifier. You might recognize them as ∀ (for all) and ∃ (there exists).


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In brief

  • Data Structures: Hash Maps! by Monday Morning Haskell

    Today we’re taking the next logical step in the progression and looking at Hash Maps. Starting later this week, we’ll start looking as lesser-known Haskell structures that don’t fit some of the common patterns we’ve been seeing so far!

  • Episode 15 by Facundo Dominguez

    Facundo Dominguez is interviewed by Niki Vazou and Joachim Breitner. Facundo Dominguez tells us the difference between STM and SMT.

  • Haskell Foundation board minutes, July 14, 2022 by Théophile Choutri

    You can check out the minutes and agenda for the Board meeting that took place on the 2022-07-14.

  • Haskell Foundation DevOps Weekly Log, 2022-07-15 by Bryan Richter

    This week I moved into phase 2 of CI failure reporting. Following on last week’s CI failure dashboard, I’m now working on a system to backfill new errors as they are categorized.

Show & tell

  • effectful: an easy to use, performant extensible effects library by Andrzej Rybczak

    Hey everyone, It’s taken ages, but finally the initial release of the effectful library is here.

  • filepath- released by Julian Ospald

    This release implements support for the “abstract filepath proposal” (AFPP). There are no breaking changes in the existing API.

  • ghc-plugin-non-empty by Dmitrii Kovanikov

    GHC Compiler Plugin for automatically converting list literals to the NonEmpty type from the Data.List.NonEmpty module in base.

  • servant-oauth2: first release by Noon van der Silk

    It’s a light-weight wrapper around wai-middleware-auth, but done within the context of “modern servant”, so you can lift authentication/authorisation information to the type level.

  • stargaze-cli by Qiao Wang

    Stargaze is a CLI tool to help you manage your starred projects on GitHub.

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