SKI in TS

An implementation of a parser, evaluator, printer, and visualizer for SKI.

Project Dependencies

• TypeScript
• Deno
• Rust (compiled to WebAssembly)
• Nix (build orchestration)

Development Setup

VS Code Extensions

This project includes VS Code workspace settings that require the following extensions:

• Deno - Official Deno extension for TypeScript support, linting, and IntelliSense

The .vscode/settings.json file configures:

• Enables the Deno extension for this workspace
• Disables the built-in TypeScript language server to avoid conflicts
• Configures Deno linting and import suggestions

Installation

1. Install the Deno extension in VS Code
2. Clone the repository
3. Open the project in VS Code - the workspace settings will automatically apply

Artifacts

• JSR

Build System

This project uses Nix for reproducible builds and version management. The build system orchestrates Rust → WASM → TypeScript builds with a single source of truth for versioning.

Note: The nixpkgs input tracks nixos-unstable branch, with the exact commit pinned in flake.lock for reproducibility. To update to a newer nixpkgs revision, run nix flake update.

Quick Start with Nix

Build everything:

nix build --extra-experimental-features 'nix-command flakes'

Enter development shell:

nix develop --extra-experimental-features 'nix-command flakes'

Run tests:

nix run .#test --extra-experimental-features 'nix-command flakes'      # Deno tests
nix run .#test-rust --extra-experimental-features 'nix-command flakes'  # Rust unit tests

Deno commands (using Nix-provided Deno):

nix run .#fmt -- --check          # Check formatting
nix run .#lint                     # Run linter
nix run .#publish -- --dry-run     # Dry run publish

Update version and generate Cargo.toml:

nix run .#update-version --extra-experimental-features 'nix-command flakes'
nix run .#generate-cargo --extra-experimental-features 'nix-command flakes'

Setting Up Nix

To avoid typing --extra-experimental-features every time, add to ~/.config/nix/nix.conf:

experimental-features = nix-command flakes

Build Artifacts

After nix build, WASM files are available at:

• result/wasm/debug.wasm - Debug WASM (1.6MB)
• result/wasm/release.wasm - Release WASM (21KB)

To copy to source tree:

cp result/wasm/*.wasm wasm/

Development Tasks

Building

With Deno (legacy):

# Build both debug and release versions
deno task build

# Build individual versions
deno task build:debug
deno task build:release

Note: For Nix builds, see the Quick Start with Nix section above.

Testing

With Deno:

# Run tests only
deno task test

# Run full CI pipeline (build + test)
deno task ci

Note: For Nix testing, use nix run .#test (see Quick Start with Nix above).

Publishing (Dry Run)

JSR (using Nix-provided Deno):

nix run .#publish -- --dry-run --allow-dirty

Crates.io:

cd rust
cargo publish --dry-run --no-verify

Available Tasks

• build - Build both debug and release WASM modules (Deno)
• build:debug - Build debug version only (Deno)
• build:release - Build release version only (Deno)
• test - Run the test suite
• ci - Run full CI pipeline (build then test)

Embedding WASM for Bundles

The CLI bundle and compiled binaries load the arena evaluator from an embedded WASM payload so they can run without filesystem or network access. After building the Rust artifacts (e.g. via nix build or deno task build), update the embedded module with:

deno run -A scripts/embed-wasm.ts

CI runs this script automatically, but local builds should run it whenever the WASM artifacts change to keep lib/evaluator/arenaWasm.embedded.ts in sync.

Interactive Development

You can experiment with the library interactively using Deno's REPL:

deno repl --allow-read

Quick Start

import {
  arenaEvaluator,
  parseSKI,
  prettyPrintSKIExpression,
} from "jsr:@maxdeliso/typed-ski";

const expr = parseSKI("(K S) I");
const result = arenaEvaluator.reduce(expr);
console.log(prettyPrintSKIExpression(result)); // "S"

For a comprehensive library of curated examples, see the JSR module documentation.

Works Referenced

Books

• Combinators: A Centennial View, Stephen Wolfram
• To Mock a Mockingbird, Raymond Smullyan
• Combinatory Logic Volume I, Haskell Brooks Curry & Robert Feys

Papers

• D. A. Turner, "A new implementation technique for applicative languages," Software: Practice and Experience, vol. 9, no. 1, pp. 31-49, 1979. DOI: 10.1002/spe.4380090105
• W. Stoye, T. J. W. Clarke, and A. C. Norman, "Some practical methods for rapid combinator reduction," in Proceedings of the 1984 ACM Symposium on LISP and Functional Programming (LFP '84), ACM, New York, NY, USA, pp. 159-166, 1984. DOI: 10.1145/800055.802038
• H. G. Baker, "CONS should not CONS its arguments, or, a lazy alloc is a smart alloc," ACM SIGPLAN Notices, vol. 27, no. 3, pp. 24-34, 1992. DOI: 10.1145/130854.130858

Troubleshooting

Nix Issues

"command not found: nix"

. /nix/store/*/etc/profile.d/nix.sh

"Git tree is dirty" This is just a warning. The build will still work.

"builder failed" Check the full log:

nix-store -l /nix/store/*-typed-ski.drv

CI/CD

GitHub Actions automatically:

1. Install Nix
2. Generate version files
3. Build Rust → WASM
4. Run tests
5. Publish to JSR and crates.io

Status