pub fn sqr<T>(x: T) -> T::Output
where T: std::ops::Mul + Copy
{
    x * x
}

fn main() {
    let a = 4_u32;
    let a_sqr = sqr(a);
    println!("u32: {}", a_sqr);

    let b = 4_f64;
    let b_sqr = sqr(b);
    println!("f64: {}", b_sqr);
}