fn round(n: f64, precision: u32) -> f64 {
    (n * 10_u32.pow(precision) as f64).round() / 10_i32.pow(precision) as f64
}

fn precision(x: f64) -> u32 {
    for digits in 0..std::f64::DIGITS {
        if round(x, digits) == x {
            return digits;
        }
    }
    return std::f64::DIGITS;
}

fn main() {
    let x = 1.0005_f64;

    println!("{:?}", precision(x));
}