# ZEN Expression Language

**The expression language of [ZEN Engine](https://crates.io/crates/zen-engine)**, the open-source [Business Rules Engine (BRE)](https://gorules.io) from [GoRules](https://gorules.io).

[![License: MIT](https://img.shields.io/badge/License-MIT-blue.svg)](https://opensource.org/licenses/MIT)
[![crates.io](https://img.shields.io/crates/v/zen-expression.svg)](https://crates.io/crates/zen-expression)

ZEN expressions are readable by business users and fast enough for hot paths: a complete language for conditions, calculations and data transformation, with lexer, parser, compiler, VM, type checking and editor completions included in this crate.

```rust
use serde_json::json;
use zen_expression::evaluate_expression;

fn main() {
    let result = evaluate_expression(
        "sum(items) * multiplier",
        json!({ "items": [10, 20, 30], "multiplier": 2 }).into(),
    )
    .unwrap();
    // => 120
}
```

Reusable expressions compile once via `compile_expression` and evaluate repeatedly against different contexts.

## Resources

- [ZEN Expression Language reference](https://docs.gorules.io/learn/zen-language/syntax) - syntax, [operators](https://docs.gorules.io/learn/zen-language/operators), [built-in functions](https://docs.gorules.io/learn/zen-language/functions) and [date operations](https://docs.gorules.io/learn/zen-language/dates)
- [ZEN Engine](https://github.com/gorules/zen) - the rules engine built on this language
- [GoRules](https://gorules.io) - the platform around the open-source engine
- [Online Editor](https://editor.gorules.io) - try expressions in the free editor with a built-in simulator

## License

[MIT License](https://opensource.org/licenses/MIT)