RosettaCodeData/Task/Cumulative-standard-deviation/Sidef/cumulative-standard-deviation-2.sidef

func stddev(x) {
    static(num=0, sum=0, sum2=0)
    num++
    sqrt(
        (sum2 += x**2) / num -
        (((sum += x) / num)**2)
    )
}
 
%n(2 4 4 4 5 5 7 9).each { say stddev(_) }