func dif(arr) {
    gather {
        range(0, arr.end-1).each { |i|
            take(arr[i+1] - arr[i]);
        }
    }
}

func difn(n, arr) {
    n.times { arr = dif(arr) };
    arr;
}

say dif([1, 23, 45, 678]);       # => [22, 22, 633]
say difn(2, [1, 23, 45, 678]);   # => [0, 611]