Ziku

A functional programming language exploring the duality between data and codata.

Features

• Pattern matching for data types
• Copattern matching for codata types using # (self-reference)
• First-class control with label/goto
• Hindley-Milner type inference with let-polymorphism
• Scheme backend for compilation to Chez Scheme

Quick Start

Docker (Recommended)

No local dependencies required:

docker build -t ziku .              # Build image
docker run --rm -it ziku lake exe ziku  # Run REPL
docker run --rm ziku                # Run tests

Native

Requires Lean 4 and Chez Scheme:

lake build              # Build
lake exe ziku           # Run REPL
make -j4 test-parallel  # Run tests

Examples

// Arithmetic and let bindings
let x = 10 in x + 1

// Functions
let double = \x => x * 2 in double 5

// Recursion
let rec factorial = \n =>
  if n == 0 then 1
  else n * factorial (n - 1)
in factorial 5

// Codata: define by behavior, not construction
// #.x => 10 means "when .x is accessed, return 10"
let point = { #.x => 10, #.y => 20 } in
point.x + point.y

// Callable codata (functions are codata!)
// #(x) => ... means "when called with x, return ..."
let square = { #(x) => x * x } in
square(5)

// Early return with label/goto
label done {
  if condition then goto(result, done)
  else continue
}

Documentation

• Getting Started - Installation and first steps
• Tutorial - Learn Ziku step by step
• Reference - Complete language reference
• Internals - Implementation details
• Development Workflow - Our GitHub-First development process

For Developers

Dependency Management

This project uses Renovate for automated dependency updates.

Renovate Setup (for maintainers):

1. Create a GitHub App

   GitHub Settings → Developer settings → GitHub Apps → New GitHub App

   Required settings:

   • GitHub App name: renovate-ziku (or any name)
   • Homepage URL: https://github.com/takoeight0821/ziku
   • Webhook: Uncheck "Active"

   Repository permissions (set all of the following):

   • Checks: Read and write
   • Contents: Read and write
   • Commit statuses: Read and write
   • Issues: Read and write
   • Pull requests: Read and write
   • Workflows: Read and write
   • Metadata: Read only (auto-set)

   After creation:

   • Note the App ID (needed later)
   • Click Generate a private key to download the .pem file

2. Install the App to the repository

   From the GitHub App page:

   • Install App → Only select repositories → Select takoeight0821/ziku
   • Get the Installation ID from the URL after installation
     • Example: 12345678 from https://github.com/settings/installations/12345678

3. Add secrets to GitHub Actions

   Repository Settings → Secrets and variables → Actions → New repository secret:

   • RENOVATE_APP_ID: The App ID from step 1
   • RENOVATE_APP_PRIVATE_KEY: The entire contents of the downloaded .pem file

4. Verify

   Actions → Renovate → Run workflow to trigger manually

Auto-updated dependencies:

• GitHub Actions (weekly, Mondays 9:00 UTC)
• Nix flake inputs (nixpkgs, flake-utils)
• Git submodules
• Lean toolchain
• Lake dependencies

See CLAUDE.md for detailed dependency management information.

Background

Ziku is inspired by "Grokking the Sequent Calculus" (ICFP 2024), implementing a λμμ̃-calculus based intermediate representation that makes the duality between data and codata explicit.

License

See LICENSE file.