Lemma Engine

Logic for man and machine

A declarative logic language engine for expressing rules, facts, and business logic in a way that is both human-readable and machine-executable.

Features

• Declarative syntax - Express rules naturally
• Type-safe units - Built-in support for money, mass, length, time, etc.
• Rule composition - Reference other rules and documents
• Conditional logic - Unless clauses for business rules
• Date arithmetic - Native datetime operations
• WebAssembly - Run in the browser

Quick Start

use lemma::{Engine, LemmaResult};

fn main() -> LemmaResult<()> {
    let mut engine = Engine::new();

    engine.add_lemma_code(r#"
        doc pricing
        fact base_price = 100 USD
        fact quantity = 5
        rule total = base_price * quantity
    "#, "pricing.lemma")?;

    let response = engine.evaluate("pricing", vec![])?;
    println!("{:#?}", response);

    Ok(())
}

Documentation

• API docs: Run cargo doc --open or visit docs.rs
• Language guide: Lemma language documentation
• Examples: Complete examples

WebAssembly

Build for use in browsers and Node.js:

node wasm/build.js

Or install from NPM:

npm install @benrogmans/lemma-engine

See wasm/README.md for detailed JavaScript API documentation.

License

Apache 2.0