e taylor series

gistfile1.rs

fn main() {
    let n = 35;
    let mut e: f64 = 1.0;
    for i in 1..n { e += (1.0 / factorial(i) as f64); }
    println!("e value: {}", e);
}

fn factorial(mut n: u128) -> u128 {
    let mut r = 1;
    for i in 2..n+1 { r *= i; }
    println!("fac({}) = {}", n, r);
    return r;
}