An exercise of Chaper 3 of the Book

fib.rs

use std::io;

fn main() {
    loop {
        println!("Input a number!");
        let mut nth = String::new();
        io::stdin()
            .read_line(&mut nth)
            .expect("Error in reading nth");
        let nth: u32 = match nth.trim().parse() {
            Ok(n) => n,
            Err(_) => continue,
        };
        let ans = fib(nth);
        println!("{}th Fibonacci number is {}", nth, ans);
    }
}

// Returns the nth number of the Fibonacci sequence.
fn fib(n: u32) -> u64 {
    match n {
        0 => 1,
        1 => 1,
        m => fib(m - 1) + fib(m - 2),
    }
}