This is an online book covering the lower level topics involved in writing an interpreter in Rust including:

• memory management: allocation and garbage collection
• compiling: expressions, functions, closures
• virtual machines: bytecode, instruction dispatch

From CPython to Ruby's YARV, V8 and SpiderMonkey, GHC to the JVM, most language runtimes are written in C/C++.

We believe that Rust is eminently suitable for implementing languages and can provide significant productivity improvements over C and C++ while retaining the performance advantages and low level control of both.

While there are a number of languages implemented in Rust available now, in varying states of completeness - interpreters, AOT compilers and JIT-compiled - our vision is singular:

To create a well documented reference compiler and runtime, permissively licensed, such that you can fork and morph it into your own programming language.

That is, a platform for bootstrapping other languages, written in Rust. To that end, the implementation provided here is not intended to be feature complete and cannot possibly represent every variation of programming language or local optimization.

It is a lofty goal, and it certainly won't be the right approach for everybody. However, we hope it will help shift the landscape in favor of more memory-safe language implementations.

See CONTRIBUTING.md for licensing and how to get involved.

The rendered book can be read here while the accompanying source code can be browsed in this repository.