kcrt

function erf(x){
    // erf(x) = 2/sqrt(pi) * integrate(from=0, to=x, e^-(t^2) ) dt
    // with using Taylor expansion, 
    //        = 2/sqrt(pi) * sigma(n=0 to +inf, ((-1)^n * x^(2n+1))/(n! * (2n+1)))
    // calculationg n=0 to 50 bellow (note that inside sigma equals x when n = 0, and 50 may be enough)
    var m = 1.00;
    var s = 1.00;
    var sum = x * 1.0;
    for(var i = 1; i < 50; i++){
        m *= i;