Loops in Functional Programming

//Functional Programming
func sum(start: Int, end: Int, total: Int) -> Int {
    if (start > end) {
        return total;
    }
    return sum(start: start + 1, end: end, total: total + start)
}
print("Functional: total: ", sum(start: 1, end: 10, total: 0)); // prints 55