round a number to the nearest thousandth in rust

main.rs
use num_traits::Float;

fn round_to_thousandth(x: f32) -> f32 {
    let precision = 3;
    let p = f32::pow(10.0, precision);
    (x * p).round() / p
}

fn main() {
    let x = 1.23456789;
    let y = round_to_thousandth(x as f32);
    println!("{} rounded to the nearest thousandth is {}", x, y);
}
300 chars
14 lines

main.rs
1.23456789 rounded to the nearest thousandth is 1.235
54 chars
2 lines