Fibonacci.rs

use std::io;

fn main() {
    println!("Enter -1 to exit");
    loop {
        let n = get_isize("Enter a number: ");
        if n == -1 {
            break;
        }
        println!("fibonacci of {} is {}", n, fibonacci(n));
    }
}

fn factorial(n: isize) -> isize {
    // base case
    if n == 0 {
        1
    } else {
        // recursive case
        n * factorial(n - 1)
    }
}

fn fibonacci(n: isize) -> isize {
    // base cases
    if n == 0 {
        0
    } else if n == 1 {
        1
    } else {
        fibonacci(n - 1) + fibonacci(n - 2)
    }
}

fn get_isize(prompt: &str) -> isize {
    print!("{}", prompt);
    let mut input = String::new();
    io::stdin()
        .read_line(&mut input)
        .expect("Failed to read line");
    input.trim().parse().expect("Please type a number!")
}