Tree-walking interpreter implementation of santa-lang, written in TypeScript.

santa-lang is a functional, expression-oriented programming language designed for solving Advent of Code puzzles. This TypeScript implementation provides:

• Tree-walking interpreter with tail-call optimization (TCO)
• Persistent immutable data structures
• First-class functions and closures
• Lazy sequences and infinite ranges
• Pattern matching with guards
• 70+ built-in functions
• AoC runner with automatic input fetching

docker pull ghcr.io/eddmann/santa-lang-prancer:cli-latest
docker run --rm ghcr.io/eddmann/santa-lang-prancer:cli-latest --help

Download pre-built binaries from GitHub Releases:

Try santa-lang in your browser: eddmann.com/santa-lang-prancer

Lambda layer available: santa-lang-prancer-lambda-{version}.zip

# Run a solution
santa-cli solution.santa
# Run tests defined in a solution
santa-cli -t solution.santa
# Evaluate inline code
santa-cli -e '1 + 2'
# Interactive REPL
santa-cli -r

Here's a complete Advent of Code solution (2015 Day 1):

input: read("aoc://2015/1")
part_one: {
  input |> fold(0) |floor, direction| {
    if direction == "(" { floor + 1 } else { floor - 1 };
  }
}
part_two: {
  zip(1.., input) |> fold(0) |floor, [index, direction]| {
    let next_floor = if direction == "(" { floor + 1 } else { floor - 1 };
    if next_floor < 0 { break index } else { next_floor };
  }
}
test: {
  input: "()())"
  part_one: -1
  part_two: 5
}

Key language features shown:

• input: / part_one: / part_two: - AoC runner sections
• |> - Pipeline operator (thread value through functions)
• fold - Reduce with early exit support via break
• test: - Inline test cases with expected values

Requires Bun or use Docker:

# Install dependencies
make lang/install
make cli/install
# Run tests
make lang/test
make cli/test
# Build CLI binaries
make cli/build

Run make help to see all available targets:

make help          # Show all targets
make shell         # Interactive shell in Docker build environment
make lang/test     # Run language tests
make cli/test      # Run CLI tests
make cli/build     # Build CLI binaries
make web/build     # Build web application
make lambda/build  # Build Lambda layer

├── src/
│   ├── lang/              # Core language library
│   │   ├── lexer/         # Tokenization
│   │   ├── parser/        # AST construction
│   │   └── evaluator/     # Tree-walking interpreter
│   ├── cli/               # Command-line interface
│   ├── web/               # Web application (Next.js)
│   └── lambda/            # AWS Lambda runtime
└── examples/              # Example AoC solutions

• eddmann/santa-lang - Language specification/documentation
• eddmann/santa-lang-editor - Web-based editor
• eddmann/santa-lang-prancer - Tree-walking interpreter in TypeScript (Prancer)
• eddmann/santa-lang-comet - Tree-walking interpreter in Rust (Comet)
• eddmann/santa-lang-blitzen - Bytecode VM in Rust (Blitzen)