How do you set the cout locale to insert commas as thousands separators?

Question

Given the following code:

cout << 1000;

I would like the following output:

1,000

This can be done u

Answer 1

The default implementation of do_thousands_sep already returns ','. It looks like you should override do_grouping instead. do_grouping returns an empty string by default, which means no grouping. This means groups of three digits each:

string do_grouping() const
{
    return "\03";
}