Haskell Weekly

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.

Featured

• Actually, Maybe is Great by Dave Della Costa

  Maybe lets us avoid the hazards and frustration in dealing with NULL values, and helps us eliminate boilerplate significantly.

• Bootstrapping a community via hackathons by Don Stewart

  I recently gave an interview to Jasper Van der Jeugt as part of the Haskell Zurich Meetup, on the history of hackathons in the Haskell community.

• Code Pray Love: Interview with Oli Makhasoeva by Denis Oleynikov

  We talk about their experience organizing Haskell Love, how they kept it accessible for developers of all levels, and what things one should definitely keep in mind when organizing an online conference.

• Dynamic scoping is an effect, implicit parameters are a coeffect by Edward Z. Yang

  Implicit parameters have a reputation of being something you shouldn’t use, whereas dynamic scoping via the reader monad is a useful and well understood construct. Why the difference?

• Finger Trees Explained Anew, and Slightly Simplified (Functional Pearl) by Koen Claessen

  We explicitly motivate the subtle intricacies of Hinze and Paterson’s Finger Tree datastructure, by step-wise refining a naive implementation.

• Handing over ghcide to the Haskell community by Moritz Kiefer

  Digital Asset has made the decision to turn ghcide into a proper community project under the haskell github organization.

• Haskell from 0 to IO (Maybe Hero)

  This guide references some syntax and patterns used when writing programs in the Haskell language.

• Implementing a GHC Plugin for Liquid Haskell by Alfredo Di Napoli

  In this blog post we’ll explore how we turned LiquidHaskell into a GHC Plugin, and all the challenges we had to overcome along the way.

• Un-obscuring a few GHC type error messages by Ziyang Liu

  Some of the GHC type error messages that can potentially lead to bewilderment are discussed in this post.

• WebUI for Haskell tooling! by Csaba Hruska

  This time I’d like to tell the story why and how I learned to build web UI based compiler tools.

Jobs

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

In brief

• Fixed points of indexed functors by Oleg Grenrus

  I was lately thinking about fixed points, more or less.

• Interactive Reanimate playground by David Himmelstrup

  Here you can write Haskell code and have it render directly to your browser.

• LTS 16 uses ghc-8.8.4 as of LTS 16.12 by Dan Burton

  LTS 16.12, the latest update to LTS 16, includes an upgrade from ghc-8.8.3 to ghc-8.8.4.

• Monthly Hask Anything (September 2020)

• Should Purescript’s Partial instead be called Unsafe? by Henri Tuhola

  Purescript’s partial functions aren’t observable in this way though, they may become preconditions that aren’t encoded in the type at the moment.

Show & tell

• Accelerate version 1.3 by Trevor McDonell

  This release includes many quality-of-life improvements for defining and using your own data types in embedded code.

• cabal-fmt version 0.1.4 by Oleg Grenrus

  cabal-fmt-0.1.4 is a small release. I made --no-cabal-file to scratch my itch, and fragments partly to highlight that not every feature can exist in Cabal, but is very fine for preprocessors.

• Clickhouse-haskell by Shi You

  ClickHouse Haskell Driver with HTTP and native (TCP) interface support.

• graphql-client by Brandon Chinn

  A client for Haskell programs to query a GraphQL API.

• hspec-expectations-json by Freckle

  Hspec expectations for JSON values.

• Supernova by Gabriel Volpe

  Apache Pulsar client for Haskell.

Call for participation

• graphql-engine: cli: support absolute paths in –envfile
• mu-haskell: How to represent oneof with a schema/use oneof in .proto files?