#!/usr/bin/ruby

func gcd(a,b) {
    b.is_zero ? abs(a) : gcd(b, a % b)
}

for (12..15) {     |x|
    for (29..30) { |y|
        say "gcd(#{x}, #{y}) == #{gcd(x, y)}"
        assert_eq(gcd(x, y), [x,y].gcd)
    }
}