Link Calculator

A grammar-based expression calculator with DateTime and Currency support, built with Rust WebAssembly and React.

Live Demo

https://link-assistant.github.io/calculator/

Screenshots

Main Interface

Arithmetic Operations

DateTime Calculations

Currency Conversions

📖 See USE-CASES.md for more detailed examples with screenshots, including symbolic integration, math functions, dark theme, and more.

Features

Expression Parser

• Arithmetic operations: +, -, *, / with proper operator precedence
• Parentheses for grouping: (2 + 3) * 4
• Negative numbers: -5 + 3
• Decimal precision using rust_decimal

DateTime Support

Supports multiple date and time formats:

• ISO format: 2026-01-22
• US format: 01/22/2026
• European format: 22/01/2026
• Month names: Jan 22, 2026, 22 Jan 2026
• Time formats: 8:59am, 14:30, with timezone support (8:59am UTC)
• DateTime arithmetic: (Jan 27, 8:59am UTC) - (Jan 25, 12:51pm UTC)

Currency Support

• Currency amounts: 84 USD, 34 EUR
• Currency arithmetic with automatic conversion: 100 USD + 50 EUR
• Temporal awareness: 84 USD - 34 EUR at 22 Jan 2026
• Support for 50+ currencies including major world currencies, precious metals, and cryptocurrencies

Links Notation

All expressions are represented in links-notation format:

• Step-by-step calculation explanations
• Issue prefill links for unrecognized input

Example Usage

> 2 + 3
Result: 5
Links notation: ((2) + (3))

> (Jan 27, 8:59am UTC) - (Jan 25, 12:51pm UTC)
Result: 1 day, 20 hours, 8 minutes
Links notation: (((Jan 27, 8:59am UTC) - (Jan 25, 12:51pm UTC)))

> 84 USD - 34 EUR
Result: 47.042 USD
Links notation: (((84 USD)) - ((34 EUR)))

Technical Implementation

Rust WASM Core (src/)

• grammar/ - Lexer and recursive descent parser
• types/ - Value, Decimal, DateTime, Currency, Unit types
• lino/ - Links notation representation
• error/ - Error types with thiserror
• wasm.rs - WebAssembly bindings

React Frontend (web/)

• Vite + TypeScript + React 18
• Web Worker for non-blocking WASM calculations
• Responsive design with real-time results
• Example expressions for quick testing

CI/CD (.github/workflows/)

• ci.yml - Tests, linting, formatting, WASM build
• deploy.yml - GitHub Pages deployment

Development Setup

Prerequisites

• Rust 1.70+ with wasm32-unknown-unknown target
• Node.js 18+
• wasm-pack

Build & Run

# Clone the repository
git clone https://github.com/link-assistant/calculator.git
cd calculator

# Build the WASM package
wasm-pack build --target web --out-dir web/public/pkg

# Install web dependencies
cd web
npm install

# Start development server
npm run dev

Running Tests

# Run all Rust tests
cargo test

# Run tests with verbose output
cargo test --verbose

# Run Clippy lints
cargo clippy --all-targets --all-features

# Format code
cargo fmt

# Check formatting (CI style)
cargo fmt --check

Building for Production

# Build optimized WASM
wasm-pack build --target web --release --out-dir web/public/pkg

# Build web frontend
cd web
npm run build

Project Structure

.
├── .github/workflows/      # CI/CD pipeline configuration
├── data/                   # Currency exchange rate databases
│   └── exchange_rates/     # Historical exchange rates (.lino files)
├── docs/                   # Documentation and screenshots
├── src/                    # Rust source code
│   ├── grammar/            # Lexer, parser, and grammar modules
│   ├── types/              # Core types (Value, DateTime, Currency, etc.)
│   ├── lino/               # Links notation module
│   ├── error.rs            # Error types
│   ├── lib.rs              # Library entry point
│   ├── main.rs             # CLI entry point
│   └── wasm.rs             # WASM bindings
├── tests/                  # Integration tests
├── web/                    # React frontend
│   ├── src/                # TypeScript source
│   └── public/             # Static assets
├── Cargo.toml              # Rust project configuration
└── README.md               # This file

Contributing

Contributions are welcome! Please see CONTRIBUTING.md for guidelines.

Development Workflow

1. Fork the repository
2. Create a feature branch: git checkout -b feature/my-feature
3. Make your changes and add tests
4. Run quality checks: cargo fmt && cargo clippy && cargo test
5. Add a changelog fragment
6. Commit your changes (pre-commit hooks will run automatically)
7. Push and create a Pull Request

License

Unlicense - Public Domain

This is free and unencumbered software released into the public domain. See LICENSE for details.

Acknowledgments

• Built with Rust and WebAssembly
• Inspired by links-notation
• React frontend powered by Vite