coil

coil is a statically typed scripting language with type inference. Programs are compiled to bytecode and executed on a custom virtual machine. Source files use the .hy extension (short for henry, the SI unit of inductance — the measure of a coil); compiled archives are stored as .hyc files.

For developers who want a small typed scripting language with more structure than a typical script, and a bytecode runtime they can keep thin.

The language targets embeddable scripting: you get real type checking and inference without a heavyweight build pipeline, plus optional FFI for calling into C libraries or host-provided Rust closures.

Quick start#

Download the toolkit for your OS. When a GitHub Release exists, use GitHub Releases (latest). There is no tagged release yet. Until then, the current build is the latest release-binaries workflow on main (binaries-<triple> artifacts, 30-day retention). See Getting Started.

use io::{stdout};
use io::sync::{write_all};
use string::{to_bytes};
fn main() {
    write_all(stdout(), to_bytes("hello"));
}

With coil on your PATH, from a clone of the repository with coil-stdlib cloned beside it:

coil --root ../coil-stdlib/src examples/print_literal.hy

Expected output: hello

How programs run#

Parse → typecheck → typed HIR (inlining, optimization passes) → stack IL + MIR tiers / lower/fuse-select → bytecode → VM executes main. coil <file.hy> compiles in memory on every run; coil compile writes a versioned .hyc archive (packed major.minor) that coil run executes. Full stage notes: Internals — Pipeline.

Language at a glance#

Browse runnable demos in Examples. Multi-file showcase apps (todo board, text adventure, TCP echo) live under examples/projects/.

Documentation#

Docs are split into three trees:

Manual (tutorial)#

Full API index: Reference.

Repository layout#

coil/
├── common/          # Shared types: opcodes, values, archive format
├── parser/          # Pratt parser and AST
├── compiler/        # Typechecker, HIR optimizations, stack IL / MIR lowering, pipeline
├── machine/         # VM, heap/GC, FFI (libffi)
├── coil-*/          # CLI helpers: test, fmt, lsp, debug, dissect, verify, embed
├── examples/        # Runnable .hy demos (see manual/examples.md)
│   └── projects/    # Showcase multi-file apps + co-located tests
├── docs/internals/  # Pipeline, VM notes, grammar (user docs live on this site)
└── src/main.rs      # CLI: default build+run, compile, run, test

Running#

For FFI examples you also need libffi (e.g. libffi-dev on Debian/Ubuntu, libffi on Arch). To build from a checkout, see Getting Started.

Learn by example#

Source for the language is ardax-corp/coil-lang. Internals stay in that repository.