Calculates factorial of a number.

Cargo.toml

[package]
name = "factorial"
version = "0.1.0"
authors = ["qolop <mptm98@gmail.com>"]

[dependencies]
num="*"

factorial_biguint.rs

extern crate num;

use num::{FromPrimitive, BigUint, One};
use std::io;

fn main() {

    println!("Please input the factorial.");

    let mut s = String::new();

    io::stdin()
        .read_line(&mut s)
        .expect("failed to read line");

    let n: u16 = s.trim().parse().expect("Enter in a positive integer only");
    println!("Factorial of {} = {}", n, factorial(n));
}


fn factorial(n: u16) -> BigUint {
    let mut f: BigUint = One::one();
    for i in 1..n+1 {
        let bu: BigUint = FromPrimitive::from_u16(i).unwrap();
        f = f * bu;
    }
    f
}