struct Rectangle {
    width: f64,
    height: f64,
}

impl Rectangle {
    fn area(&self) -> f64 {
        self.width * self.height
    }

    fn scale(&mut self, factor: f64) {
        self.width *= factor;
        self.height *= factor;
    }
}

fn main() {
    let mut r = Rectangle{ width: 5.0, height: 2.5 };
    println!("Area of rectangle is {}", r.area());
    r.scale(1.25);
    println!("Area of scaled up rectangle is {}", r.area());
}