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9 March 2023 — by Erin van der Veen, Nicolas Bacquey, Guillaume Genestier, Christopher Harrison, , Tor Hovland Topiary aims to be a universal formatter engine within the Tree-sitter ecosystem. Named after the art of clipping or trimming trees into fantastic shapes, it is designed for formatter authors and formatter users: Authors can create a formatter for a language without having to write their

On most systems, you can implement concurrency using either threads or processes, where the main difference between the two is that threads share memory and processes don’t. Modern web browsers support concurrency through the Web Workers API. Although Web Workers are by default closer to a multi-process model, when used with WebAssembly you can opt-in to a more thread-like experience. Just like in

Tweag has been working on a GHC WebAssembly backend for some time. Recently, the WebAssembly backend merge request has landed in GHC, and is on course to appear in the upcoming 9.6 release series. This post will give a quick demonstration of how to try it out locally, and explain what comes in this patch and what will be coming next. Playing with WASM locally If you’re using nix on x86_64-linux, c

You may be aware of Nix or NixOS. Users love them for being superior tools for building, deploying, and managing software. Yet, Nix is generally perceived as notoriously hard to learn. The core Nix ecosystem consists of several distinct components: Nix is a build system and package manager that comes with a configuration language to declare software components, the Nix language. Software made avai

Since the inception of the Haskell language, the community around it has steadily innovated with language extensions and abstractions. To mention a few, we had the IO monad, all flavors of type classes and constraints, Template Haskell, generalized algebraic data types (GADTs), data kinds, etc. Then we had to deal with the programs resulting from all this innovation, which eventually sprang feelin

This is the first in a series of blog posts intended to provide a gentle introduction to flakes, a new Nix feature that improves reproducibility, composability and usability in the Nix ecosystem. This blog post describes why flakes were introduced, and give a short tutorial on how to use them. Flakes were developed at Tweag and funded by Target Corporation and Tweag. What problems do flakes solve?

We’re announcing linear-base, a standard library for Linear Haskell programs. Our release accompanies the release of GHC 9.0 which supports -XLinearTypes. Linear base has been written by Bhavik Mehta, a former Tweag intern, Arnaud Spiwack, and ourselves. In the spirit of a standard library, linear-base is not a strict replica of base with linearly-typed variants of all the facilities in base. Inst

My goal today is to convince you that destination-passing style is neat, actually. And that linear types make destination-passing purely functional. But first, I must answer a question. What is destination-passing style? If you’ve ever programmed in C, C++, or Fortran, you are sure to have encountered the style of programming which sometimes goes by the name destination-passing style. It is the pr

As a Tweag Open Source fellow, I aimed to improve and build on the Haskell IDE experience, mainly by contributing to the ghcide and haskell-language-server projects. My main goals were to polish up the overall experience, and integrate hiedb, a product of a Summer of Code project last year, into ghcide. The product of this fellowship was a good selection of ghcide and haskell-language-server featu

This can arise when you have different threads. But it’s of prime importance in a lazy language like Haskell, since it makes it possible to generate deterministic random numbers lazily. For instance, split is used in QuickCheck’s Gen monad. An easy implementation of split is to duplicate the current state. But, the two parallel sequences will not be independent: indeed they will be identical. A sl

Improving the craft of software engineeringWe are on a mission to improve developer experience (DX) and data-centric workflows (MLOps). Tweag is a collaborative space where engineers and researchers join forces to apply new ideas — all as open source. Featured ProjectsTweagers are leading contributors to several open source projects — from functional programming languages to cross-platform framewo