regex - Parsing Perl regex with golang

Question

http://play.golang.org/p/GM0SWo0qGs

This is my code and playground.

func insert_comma(input_num int) string {
    temp_str := strconv.Itoa(input_num)
    var validID = regexp.MustCompile(`\B(?=(\d{3})+$)`)
    return validID.ReplaceAllString(temp_str, ",")
}

 func main() {
    fmt.Println(insert_comma(1000000000))
 }

Basically, my desired input is 1,000,000,000. And the regular expression works in Javascript but I do not know how to make this Perl regex work in Go. I would greatly appreciate it. Thanks,

Answer 1

Since lookahead assertion seems to be not supported, I'm providing you a different algorithm with no regexp:

Perl code:

sub insert_comma {
    my $x=shift;
    my $l=length($x);
    for (my $i=$l%3==0?3:$l%3;$i<$l;$i+=3) {
        substr($x,$i++,0)=',';
    }
    return $x;
}
print insert_comma(1000000000);

Go code: Disclaimer: I have zero experience with Go, so bear with me if I have errors and feel free to edit my post!

func insert_comma(input_num int) string {
    temp_str := strconv.Itoa(input_num)
    var result []string
    i := len(temp_str)%3;
    if i == 0 { i = 3 }
    for index,element := range strings.Split(temp_str, "") {
        if i == index {
            result = append(result, ",");
            i += 3;
        }
        result = append(result, element)
    }
    return strings.Join(result, "")
}

func main() {
    fmt.Println(insert_comma(1000000000))
}

http://play.golang.org/p/7pvo7-3G-s