// An interactive "Hello, world" using Dust's built-in I/O functions
write_line("Enter your name...")

let name = read_line()

write_line("Hello " + name + "!")

// The classic, unoptimized Fibonacci sequence
fn fib (n: int) -> int {
    if n <= 0 { return 0 }
    if n == 1 { return 1 }

    fib(n - 1) + fib(n - 2)
}

write_line(fib(25))

Highlights

Easy to read and write
Single-pass, self-optimizing compiler
Static typing with extensive type inference
Multi-threaded register-based virtual machine with concurrent garbage collection
Beautiful, helpful error messages from the compiler
Safe execution, runtime errors are treated as bugs

Overview

Dust's syntax, safety features and evaluation model are based on Rust. Its instruction set and optimization strategies are based on Lua. Unlike Rust and other languages that compile to machine code, Dust has a very low time to execution. Unlike Lua and most other interpreted languages, Dust enforces static typing to improve clarity and prevent bugs.

Project Goals

This project's goal is to deliver a language with features that stand out due to a combination of design choices and a high-quality implementation. As mentioned in the first sentence, Dust's general aspirations are to be fast, safe and easy.

Fast
- Fast Compilation Despite its compile-time abstractions, Dust should compile and start executing quickly. The compilation time should feel negligible to the user.
- Fast Execution Dust should be competitive with highly optimized, modern, register-based VM languages like Lua. Dust should be bench tested during development to inform decisions about performance.
- Low Resource Usage Memory and CPU power should be used conservatively and predictably.
Safe
- Static Types Typing should prevent runtime errors and improve code quality, offering a superior development experience despite some additional constraints. Like any good statically typed language, users should feel confident in the type-consistency of their code and not want to go back to a dynamically typed language.
- Null-Free Dust has no "null" or "undefined" values. All values are initialized and have a type. This eliminates a whole class of bugs that are common in other languages.
- Memory Safety Dust should be free of memory bugs. Being implemented in Rust makes this easy but, to accommodate long-running programs, Dust still requires a memory management strategy. Dust's design is to use a separate thread for garbage collection, allowing other threads to continue executing instructions while the garbage collector looks for unused memory.
Easy
- Simple Syntax Dust should be easier to learn than most programming languages. Its syntax should be familiar to users of other C-like languages to the point that even a new user can read Dust code and understand what it does. Rather than being held back by a lack of features, Dust should be powerful and elegant in its simplicity, seeking a maximum of capability with a minimum of complexity.
- Excellent Errors Dust should provide helpful error messages that guide the user to the source of the problem and suggest a solution. Errors should be a helpful learning resource for users rather than a source of frustration.
- Relevant Documentation Users should have the resources they need to learn Dust and write code in it. They should know where to look for answers and how to reach out for help.

Author

I'm Jeff 🦀 and I started this project as simple expession evaluator. Initially, the project used an external parser and a tree-walking interpreter. After several books, a few papers, countless articles and a lot of experimentation, Dust has evolved to an ambitious project that aims to implement lucrative features with a high-quality implementation that competes with established languages.

Usage

Dust is under active development and is not yet ready for general use.

Installation

Eventually, Dust should be available via package managers and as an embeddable library. For now, the only way to use Dust is to clone the repository and build it from source.

Inspiration

Crafting Interpreters¹ by Bob Nystrom was a great resource for writing the compiler, especially the Pratt parser. The book is a great introduction to writing interpreters. Had it been discovered sooner, some early implementations of Dust would have been both simpler in design and more ambitious in scope.

The Implementation of Lua 5.0² by Roberto Ierusalimschy, Luiz Henrique de Figueiredo, and Waldemar Celes was a great resource for understanding register-based virtual machines and their instructions. This paper was recommended by Bob Nystrom in [Crafting Interpreters].

A No-Frills Introduction to Lua 5.1 VM Instructions³ by Kein-Hong Man has a wealth of detailed information on how Lua uses terse instructions to create dense chunks that execute quickly. This was essential in the design of Dust's instructions. Dust uses compile-time optimizations that are based on Lua optimizations covered in this paper.

"A Performance Survey on Stack-based and Register-based Virtual Machines"⁴ by Ruijie Fang and Siqi Liup was helpful for a quick yet efficient primer on getting stack-based and register-based virtual machines up and running. The included code examples show how to implement both types of VMs in C. The performance comparison between the two types of VMs is worth reading for anyone who is trying to choose between the two. Some of the benchmarks described in the paper inspired similar benchmarks used in this project to compare Dust to other languages and inform design decisions.

Writing a Compiler in Go⁵ by Thorsten Ball is a lot like Crafting Interpreters, they are the where I look for a generalized approach to solving a problem. Filled with code examples, this book helps the reader make the turn from evaluating a syntax tree to thinking about how problems are solved on physical hardware and how that informs the design of a virtual machine.

Let me get straight to the point: a virtual machine is a computer built with software. -- Thorsten Ball, Writing a Compiler in Go

Structure and Interpretation of Computer Programs, Second Edition⁶ by Harold Abelson and Gerald Jay Sussman with Julie Sussman is a classic text on computer science. It encourages an abstract view of programming, sometimes using diagrams to explain programs as though they were physical devices. It requires more effort than the books that immediately show you how to write a program, but the takeaway is a deep understanding of the the process a computer (or a VM) goes through to execute a program.

License

Dust is licensed under the GNU General Public License v3.0. See the LICENSE file for details.