\ Haskell Weekly \/\/ Issue 61 https://haskellweekly.news/issues/61.html Welcome to another issue of Haskell Weekly! Haskell is a purely functional programming language that focuses on robustness, concision, and correctness. This is a weekly summary of what's going on in its community. ## Featured ## - Haxl: Making concurrency unreasonably easy http://events.techcast.com/bigtechday10/Garmisch-1345/

Haxl is a big hammer for doing I/O concurrently, testing I/O, and modularity (caching & memoization).

- Introduction to Brick https://samtay.github.io/articles/brick.html

I'm going to give a short introduction to Brick, a Haskell library for building terminal user interfaces. So far I've used brick to implement Conway's Game of Life and a Tetris clone. I'll explain the basics, walk through an example snake application, and then explain some more complicated scenarios.

- Simplexhc: An STG to LLVM compiler https://pixel-druid.com/blog/announcing-simplexhc/

STG's lowering to C-- and the decisions taken when implementing it were based in the '90s. That's not to say that the GHC team hasn't done an awesome job keeping it up to date; they have! But, I wonder what a complete rewrite of this lowering would look like. Hence, I'm trying to experiment in this space and see what happens.

- Front Row is hiring a senior backend Haskell engineer https://frontrow.workable.com/j/463B843754

Come change how 6.5+ million K-12 US students learn Math, Language Arts, Social Studies and more. Use data, advanced type systems, great product design and deep pedagogy to change lives.

- Threading responsibly: `forkIO` considered harmful http://mazzo.li/posts/threads-resources.html

In this post I want to argue that threads are also a resource, in the sense that they require management after we've created them. A stray thread will consume memory, CPU cycles, and really whatever resource it might need to execute.

- The `Has` type class pattern https://medium.com/@jonathangfischoff/the-has-type-class-pattern-ca12adab70a...

The value in this approach is that I don't have to think about what functions to call to collect the images: it's always `images`. In the prior example, I had to think about the how to collect the images each time, and it took brain power better spent elsewhere.

- A tale of two brackets https://www.fpcomplete.com/blog/2017/06/tale-of-two-brackets

I hope the primary thing you take away from it is a deeper understanding of how monad transformer stacks interact with operations in the base monad, and how monad-control works in general.

- `RecordWildCards` and binary parsing https://jship.github.io/posts/2017-06-24-record-wildcards-and-binary-parsing...

`RecordWildCards` is a GHC extension that makes working with Haskell records more convenient. The extension has been blogged about in a few places already, so this post intends to provide a different motivating example: binary parsing.

- On naming things: Library design http://www.parsonsmatt.org/2017/06/23/on_naming_things.html

I've written a few libraries now and have tried out different naming and exporting conventions. I've developed a bit of a feel for how it is to write and use them, and I'm going to put out my personal preferences and opinions on library design here.

- Haskell Bits #6: A guide to mutable references http://www.kovach.me/posts/2017-06-22-mutable-references.html

There are quite a few ways to store mutable data in Haskell. Let's talk about some of them! Specifically, we will focus on mutable containers that store a single value that can be modified by one or more threads at any given time. I'm not going to go into a ton of detail here --- I just want to give an overview.

- Interfaces and type classes: Number APIs in C# and Haskell https://mzabani.wordpress.com/2017/06/22/interfaces-and-typeclasses-number-a...

In C# sometimes I sorely miss something like an `INumber<T>` interface with methods add, subtract, multiply, and others. The lack of this means it is cumbersome to write generic code on numbers.

## Package of the week ## This week's package of the week is data-has, a library that provides a simple extensible product system. https://www.stackage.org/lts-8.20/package/data-has-0.2.1.0 ## In brief ## - Announcing haskus-system 0.7 http://hsyl20.fr/home/posts/2017-06-29-announcing-haskussystem-07.html - Defeating evil with data structures https://mmhaskell.com/blog/2017/6/26/fun-with-data-structures - stack2nix first public release https://mailman.science.uu.nl/pipermail/nix-dev/2017-June/024011.html - Streaming combinators and extracting flat parallelism https://futhark-lang.org/blog/2017-06-25-futhark-at-pldi.html - Typing Nix https://www.tweag.io/posts/2017-05-23-typing-nix.html - When competing with C, fudge the benchmark https://medium.com/@n0mad/when-competing-with-c-fudge-the-benchmark-16d3a91b... ## Events ## - Berlin Functional Programming Group's first meeting July 1 https://www.meetup.com/Berlin-Functional-Programming-Group/events/241040383/ - Haskell.SG's July meetup July 5 https://www.meetup.com/HASKELL-SG/events/240959693/