Rhai is a scripting language written in and generally used by the programming language Rust when you want something a bit more dynamic/don’t want to recomile.

The Rhai book is the mdBook style documentation that describes the language, gets into how to use it (in both straight forward and more complicated scenarios), and acts as a reference when needed.

It’s a bit of an odd one to read straight through, but I’ve been looking for exactly this sort of thing (an embeddable scripting language for Rust) so I figured I’d give it a chance!

Languagewise, the upside is the tight integration with Rust. Downsides are that it will never be as fast as some things like JS or Lua, since (in addition to being a much smaller target market), it’s just a different style of language. No JIT, not even a VM. But you don’t always need that!

Bookwise, the initial introduction and examples are solid and a good introduction. Then we get a section on Rust integration which is entirely necessary but goes far further than I expect to need. The section after (‘Scripting Language’) feels a fair bit repetitive when compared to the introduction and I’d probably have swapped this and the integration section.

After that, several chapters of more advanced concepts are well placed and a deep dive into all sorts of interesting ideas both for Rhai specifically and programming language design more generally. I find the currying style built directly into functions–and then used to implement closures–to be particularly neat. I may steal that one day.

And the language reference–don’t read that straight through, that’s not what it’s for. 😄

Overall, a neat language and a neat read. Let’s see what we can do with it!