Greatest Common Divisor from a set of more than 2 integers

Question

There are several questions on Stack Overflow discussing how to find the Greatest Common Divisor of two values. One good answer shows a neat recursive function

Answer 1

let a = 3
let b = 9

func gcd(a:Int, b:Int) -> Int {
    if a == b {
        return a
    }
    else {
        if a > b {
            return gcd(a:a-b,b:b)
        }
        else {
            return gcd(a:a,b:b-a)
        }
    }
}
print(gcd(a:a, b:b))