#![allow(dead_code, deprecated, unused_variables, unused_mut)]
use std::ops::MulAssign;
#[derive(Debug, PartialEq)]
struct Frequency {
    hertz: f64,
}
impl MulAssign<f64> for Frequency {
    fn mul_assign(&mut self, rhs: f64) {
        self.hertz *= rhs;
    }
}
fn main() {
    let mut frequency = Frequency { hertz: 50.0 };
    frequency *= 4.0;
    assert_eq!(Frequency { hertz : 200.0 }, frequency);
}