Among programming languages, Haskell isn’t the most common choice (like JavaScript) or the one that makes a lot of engineers excited (like Rust).

At the same time, it has attracted a solid following in certain sub-fields of software development. Large companies like GitHub, Microsoft, Tesla, and Meta reach for the language when the necessity arises.

That’s because Haskell is best-in-class for building two things: self-contained systems of any complexity and domain-specific languages (DSLs).

In this article, I’ll look at the success stories of Haskell in areas like finance, blockchain, education, the automotive industry, and developer tooling. I’ll explain why large companies decide to use Haskell and what seems to me to be the future of the language.

Hasura is an open-source GraphQL engine that gives you instant access to a GraphQL API for your data. In the GitHub repository of Hasura, Haskell is the most used language, followed by languages like TypeScript, JavaScript, Python, and Go.

At the start of 2022, Hasura raised $100 million at a 1 billion valuation, making them the first Haskell unicorn.

A lot of what Hasura does can be boiled down to a performant JIT compiler that is presented as a web-server handling large concurrent loads. Haskell has allowed us to collaborate on a large codebase and has allowed us to move with startup-like speeds on infrastructure software without breaking things. (Source)

You can learn more about Hasura’s experience with Haskell by reading this blog post.

GitHub used Haskell for implementing Semantic, a command-line tool for parsing, analyzing, and comparing source code.

According to GitHub, Haskell is a good choice for this purpose because of Haskell’s strength in working with source code. As some of its most valuable features, they mention strong typing, lazy evaluation, purity, and the rich possibilities for users to define their own control flow.

The Semantic project is concerned with parsing, analyzing (evaluating), and comparing source code and as such we are firmly rooted in the academic domain of programming language theory (PLT) and spend significant time applying existing research to the real world problem of analyzing source code on GitHub. Haskell is well suited to this domain. Its language features allow concise, correct, and elegant expression of the data structures and algorithms we work with. (Source)

Read more about why GitHub chose to use Haskell for Semantic here.

Meta is known to be a Haskell user and is also one of the biggest sponsors of the Haskell Foundation.

There are three Haskell projects that Meta has worked on that deserve featuring:

• Sigma, an anti-abuse platform that processes more than a million requests per second.
• Glean, a system for collecting and working with facts about source code.
• Haxl, a framework for efficient and concise data fetching.

Here’s what they say about Haskell:

Haskell is a purely functional programming language that is held in high esteem in the programming community for its expressive type system, rich library ecosystem, and high-quality implementations. This combination of properties enables the rapid development of robust software with strong correctness and safety guarantees. (Source)