如何在Rust中向上或向下舍入数字？

fn main() {
    let num = 3.14;
    let ceil_num = num.ceil();
    println!("{} 向上舍入为 {}", num, ceil_num); // 输出: 3.14 向上舍入为 4.0
}

fn main() {
    let num = 3.14;
    let floor_num = num.floor();
    println!("{} 向下舍入为 {}", num, floor_num); // 输出: 3.14 向下舍入为 3.0
}

fn main() {
    let num = 3.5;
    let rounded_num = num.round();
    println!("{} 四舍五入为 {}", num, rounded_num); // 输出: 3.5 四舍五入为 4.0
}

fn main() {
    let num = 3.14;

    // 向上舍入
    let ceil_num = num.ceil();
    println!("{} 向上舍入为 {}", num, ceil_num);

    // 向下舍入
    let floor_num = num.floor();
    println!("{} 向下舍入为 {}", num, floor_num);

    // 四舍五入
    let rounded_num = num.round();
    println!("{} 四舍五入为 {}", num, rounded_num);
}