// iterators4.rs

pub fn factorial(num: u64) -> u64 {
    // Complete this function to return factorial of num
    // Do not use:
    // - return
    // For extra fun don't use:
    // - imperative style loops (for, while)
    // - additional variables
    // For the most fun don't use:
    // - recursion
    // Execute `rustlings hint iterators4` for hints.
    (1..num + 1).into_iter().fold(1, |acc, n| acc * n)
    // (1..num + 1).into_iter().fold(1, |acc, n| { let res = acc * n; println!("{} x {} = {}", acc, n, res); res })
}

#[cfg(test)]
mod tests {
    use super::*;

    // #[test]
    // fn factorial_of_1() {
    //     assert_eq!(1, factorial(1));
    // }
    // #[test]
    // fn factorial_of_2() {
    //     assert_eq!(2, factorial(2));
    // }

    #[test]
    fn factorial_of_4() {
        assert_eq!(24, factorial(4));
    }
}
