其它数学计算

大数

BigInt 使得超过 128 位的大整数计算成为可能。

use num::bigint::{BigInt, ToBigInt};

fn factorial(x: i32) -> BigInt {
    if let Some(mut factorial) = 1.to_bigint() {
        for i in 1..(x+1) {
            factorial = factorial * i;
        }
        factorial
    }
    else {
        panic!("Failed to calculate factorial!");
    }
}

fn main() {
    println!("{}! equals {}", 100, factorial(100));
}