The Bolt Programming Language

[!WARNING]

This compiler is experimental and might have breaking changes with each update. It is not even guaranteed to compile something at this moment!

💬 Got some questions or feedback? Just open an issue and we'll be glad to respond!

Try it out on our playground!

fn fac(n: i32) -> i32 {
    match n {
      0 | 1 => 1
      k => k * fac(k-1)
    }
}

Bolt is a new strictly-evaluated programming language in the making that aims to make writing complex applications dead-simple. It ships with some nice goodies, including:

• Static type checking will catch hundreds of bugs before a single line of code is actually run.
• Garbage collected, freeing you from worrying about memory management.
• Tuples, match-expressions and hygienic macros make your code more readable and concise.
• Cross-platform standard library, allowing you to write your code for the web and the desktop at the same time.

Examples

Read the tutorial to learn more!

Core Principles

Bolt has a few fundamental design principles that we hope in time will make it stand out from other programming languages.

• Do it right. From Hindley-Milner to algebraic effects, decades of research has made it possible to write programming languages that can be way more secure and performant than would have been possible in 70s. Wherever possible, we try to make use of these awesome discoveries.
• Do it once. Bolt aims to save development time. Type-based abstractions, a macro system, and a platform that works on both desktop and the web has to ensure that you don't waste time writing the same logic in a slightly different form.
• Do not constrain the user. Given that the perfect programming language theory has yet to be discovered, real-world programs may require the programmer to e.g. mutate a variable. Don't make the developer jump through hoops unless the benefits clearly outweigh the costs.

FAQ

Why is this project using AI?

It is thanks to AI that this project is back alive. See this blog post for more information.

I almost gave up on this project. In a desparate move, I tried out Claude Code, and it helped me tremendously. I judged the quality of the code Claude produces to be equal or even better than the code I write.

I still try to validate as much as I can of the code Claude produces. The test suite is growing every day, and should guarantee that the produced code is correct.

When will the compiler be ready to use?

It is really difficult to say when the compiler will be ready. This project is made exclusively in people their spare time. Depending on the availability of the programmers making this project possible, this might take a lot of months or even years.

Currently, we are working hard to get the type-checker fully operational. After that work will continue on the code generator and garbage collector. A small part of the code generator is already done: the first bindings to LLVM are operational and will be expanded in the future. Stay tuned!

Why yet another programming language?

Granted, there are a lot of programming languages, but oddly enough I found myself in the situation where I was still not completely satisfied. For example, Rust is a fantastic programming language, but writing web applications in it feels a little cumbersome due to its manual memory management. On the other hand, functional programming languages like Haskell and Idris look like they come straight out of the future, but sometimes have unpredictable run-time performance and force you to do weird things when all you want to do is mutate a variable. Bolt aims to solve these two issues, while not giving in on performance or correctness.

Why should I choose Bolt over JavaScript?

First of all, let me tell you that if you've never heard of a functional programming language, learning Bolt will take some time. However, I assure you that it is worth it.

• Correctness, because Bolt has a type system that is far superior to JavaScript's. No more member accesses into undefined or other weird error messages.
• Performance, because the language has been designed to leave room for a lot of optimisations. The garbage collector is one of the few overheads that the language requires.
• Scalability, because just like Rust, Bolt takes a functional approach to software design using type traits, favouring composition over inheritance.

What happened to the old compiler?

The old repository has been archived and has been replaced with this one. I doubt there will be much interest in this older software artifact. If you want to check it out nonetheless, you can still do it by following this link.

What's the difference between the old Bolt programming language and this language?

I redesigned the language from the ground up to be more functional, terser, and with very straightforward extensions for writing complex HTML. It is by no means done, but I do hope to have struck a good balance between readability and ease of use.

License

Bolt was initially licensed under the GNU GPL, version 3. I decided to release this new version under the more permissive MIT license. In the end, I hope that this piece of software may inspire other projects and may improve the quality of new and existing software.