#![feature(type_ascription)]

#[no_mangle]
pub extern fn fib(n: i32) -> f64 {
    let inverse_five_sqrt:f64 = 1.0/(5.0:f64).sqrt();
    let first_term = (1.0+(5.0:f64).sqrt()) / 2.0;
    let second_term = (1.0-(5.0:f64).sqrt()) / 2.0;
    (inverse_five_sqrt * first_term.powi(n) - inverse_five_sqrt * second_term.powi(n)).round()
}

fn main() {
    println!("fib 1: {}", fib(1));
    println!("fib 2: {}", fib(2));
    println!("fib 3: {}", fib(3));
    println!("fib 4: {}", fib(4));
    println!("fib 5: {}", fib(5));
    println!("fib 100: {}", fib(100));
}