Function num2str_rec

code/chapter04/num2str_rec.rs:6–13

(num: i32, base: i32)

                             "8","9","A","B","C","D","E","F"];

fn num2str_rec(num: i32, base: i32) -> String {
    if num < base {
        BASESTR[num as usize].to_string()
    } else {
        // 余数应加在末尾
        num2str_rec(num/base, base) + BASESTR[(num % base) as usize]
    }
}

fn main() {
    let num = 100; let sb = num2str_rec(num,2);