GitHub - durable-oss/amoskeag: Functional evaluation language for business rules with parser, interpreter, and spreadsheet-like standard library.

A purely functional, statically-validated evaluation language designed for high-security, sandboxed evaluation.

Overview

Amoskeag is a Domain-Specific Language (DSL) engineered from first principles for high-security, sandboxed evaluation. Its core purpose is to evaluate domain-specific logic in a provably safe, deterministic, and efficient manner.

Key Features

• Purely Functional: No side effects, no mutation, no I/O
• Statically Validated: Symbols are validated at compile-time
• Expression-Based: Everything is an expression that yields a value
• Secure by Design: Immune to SSTI and RCE vulnerabilities
• Developer-Friendly: Ruby-inspired syntax with functional composition

Use Cases

1. Business Rules Engine: Evaluate complex business logic with compile-time guarantees
2. Template Engine: Secure alternative to ERB with more power than Liquid
3. Spreadsheet Formula Engine: Formal execution model for cell formulas

Project Structure

amoskeag/
├── lib/
│   ├── amoskeag/                    # Main library (compiler & interpreter)
│   ├── amoskeag-lexer/              # Lexical analysis (tokenization)
│   ├── amoskeag-parser/             # Syntactic analysis using nom
│   ├── amoskeag-stdlib-operators/   # Standard library operators
│   ├── amoskeag-stdlib-functions/   # Standard library functions
│   └── amoskeag-jit/                # JIT compiler using LLVM
├── bin/
│   └── amoskeag-cli/                # Command-line interface
├── Cargo.toml                       # Workspace configuration
└── README.md                        # This file

Building

This project uses cargo-zigbuild for cross-platform builds.

Prerequisites

Install zigbuild:

cargo install cargo-zigbuild

Build Commands

# Standard build
cargo build

# Build with zigbuild
cargo zigbuild --release

# Run tests
cargo test

# Build for specific target
cargo zigbuild --target x86_64-unknown-linux-gnu

Building with JIT Support

The amoskeag-jit crate requires LLVM 18 with development headers:

# Ubuntu/Debian
sudo apt-get install llvm-18-dev

# macOS
brew install llvm@18

# Build with JIT support
cargo build -p amoskeag-jit

See lib/amoskeag-jit/README.md for detailed JIT compiler documentation.

Language Syntax

Example: Business Rule

let app = applicant
let limits = env.underwriting_limits

let state_is_restricted = limits.restricted_states | contains(app.state)

if state_is_restricted
  :deny
else if app.vehicle.value > limits.max_vehicle_value
  :deny
else if app.vehicle.type == 'SPORT' and app.age < 25
  :deny
else
  :approve
end

Example: Template

# String manipulation with pipe operator
post.title | upcase | truncate(50)

# Conditional rendering
if user.is_admin
  "Welcome, Admin!"
else
  "Welcome, " + user.name
end

Example: Spreadsheet Formula

# Excel-like functions
let growth_rate = choose(B1, B2)
let revenue = B3 * (1 + growth_rate)
revenue | round(2)

Core Language Features

Data Types

• Number: 64-bit floating-point
• String: UTF-8 immutable strings
• Boolean: true or false
• Nil: The nil value
• Array: Ordered, immutable list
• Dictionary: Immutable key-value map
• Symbol: Statically-validated enumeration (e.g., :approve, :deny)

Operators

• Arithmetic: +, -, *, /, %
• Comparison: ==, !=, <, >, <=, >=
• Logical: and, or, not
• Pipe: | (function chaining)
• Access: . (dictionary navigation)

Keywords

if, else, end, let, in, true, false, nil, and, or, not

License

MIT OR Apache-2.0

Documentation

See AMOSKEAG.md for the complete formal specification.