rhai/examples/simple_fn.rs

use rhai::{Engine, RegisterFn};

fn main() {
    let mut engine = Engine::new();

    fn add(x: i64, y: i64) -> i64 {
        x + y
    }

    engine.register_fn("add", add);

    if let Ok(result) = engine.eval::<i64>("add(40, 2)") {
        println!("Answer: {}", result); // prints 42
    }
}