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nemo-lang

nemo is a small procedural programming language that compiles to Wasm GC

Playground

Check out the Nemo playground for example programs. It runs entirely in your browser, so you can play around and experiment however you like.

Motivation

I "know" how to do a lot of things in compilers theoretically, conceptually, or in isolation. This project helps me verify I can actually put them together and understand them well enough to put into practice.

I think Wasm GC is a fantastic opportunity. It could make creating new high-level interesting languages fun, and accessible. Part of making that a reality is building tooling, examples, and teaching materials. I hope Nemo can help in that effort.

Depending on how the language evolves it might become part of my compilers course at TH Cologne.

Language Features

Most features can be directly mapped to Wasm GC constructs. I'm just listing them here:

  • Function imports
  • Top-level functions
  • Globals
  • Primitive types: i32, f32, bool, unit
  • Composite types: Structs (nominal), Arrays (structural)
  • if-expressions
  • while
  • Early returns
  • Infix operators for most numeric instructions
  • Built-in functions/intrinsics for all other numeric functions

Features we implement "on-top"

  • First order parametric polymorphism (Generics) via monomorphization
  • Variants & Pattern matching
  • First class functions (closures)
  • Lazy initialization for non-const globals
  • Type directed operator resolution (+ can mean both i32.add and f32.add)
  • Type directed field resolution for struct access
  • Nested set targets for composite types: set p.particles[2].vx = 10.0
  • Block scoping

Working on the project

The compiler is written in Rust, so at the minimum you'll need a Rust toolchain.

While developing the compiler a couple of other tools are useful/necessary to have:

  • just: The command runner used for tasks in the justfile
  • wasm-bindgen: Required to build the playground
  • wasm-tools: Wasm pretty printer/parser tools
  • wasm-opt: The wasm-opt tool from Emscripten packaged up as a Rust package

The easiest way I've found to install them is using cargo-binstall:

cargo binstall just wasm-bindgen-cli wasm-tools wasm-opt watchexec-cli

Additionally you'll need Deno to run the tests.