fn f1<T>(v:Option<T>) -> Option<T> {
        return v
}

fn f2<T>(v:Option<T>) -> Option<T> {
        return v
}

fn f3<T>(v:Option<T>) -> Option<T> {
        return v
}

fn f4<T>(v:Option<T>) -> Option<T> {
        return v
}

fn f5(v:Option<i32>) -> Option<i32> {
        return v
}


fn f6(v:Option<i32>) -> Option<i32> {
        return v
}
fn f7(v:Option<bool>) -> Option<bool> {
        return v
}

// This function handles a division that may not succeed
fn lucky_number(n: i32) -> Option<i32> {
    if n>5 {
      return Some(n)
    }
    return None
}

fn main() {
    match f1(f2(f3(f4(f5(lucky_number(4)))))) {
        Some(_) => println!("Good!"),
        None=> println!("Failed"),
    }

    match f1(f2(f3(f4(f5(lucky_number(10)))))) {
        Some(val) => println!("Good! You entered {}",val),
        None=> println!("Failed"),
    }

    let generic_str  = "string value";
    match f1(f2(f3(Some(generic_str)))) {
        Some(val) => println!("Good! You entered {}",val),
        None=> println!("Failed"),
    }

    let generic_bool: bool  = true;
    match f1(f2(f3(Some(generic_bool)))) {
        Some(val) => println!("Good! You entered {}",val),
        None=> println!("Failed"),
    }

    f6(f4(f5(Some(42)))); // works
//    f7(f4(f5(Some(42)))); // fails

}