std::moneypunct::grouping, do_grouping

From cppreference.com
< cpplrm; | localelrm; | moneypunct
Defined in header <locale>
public:
std::string grouping() const;
(1)
protected:
virtual std::string do_grouping() const;
(2)
1) Public member function, calls the member function do_grouping of the most derived class.
2) Returns the pattern that determines the grouping of the digits in the monetary output, with the same exact meaning as std::numpunct::do_grouping

Return value

The object of type std::string holding the groups. The standard specializations of std::moneypunct return an empty string, indicating no grouping. Typical groupings (e.g. the en_US locale) return "\003".

Example

#include <locale>
#include <iostream>
#include <iomanip>
#include <iterator>
struct space_out : std::moneypunct<char> {
    pattern do_pos_format()      const { return { {value, none, none, none} };}
    int do_frac_digits()         const { return 0; }
    char_type do_thousands_sep() const { return ' ';}
    string_type do_grouping()    const { return "\002";}
};
int main()
{
    std::cout.imbue(std::locale("en_US.UTF-8"));
    std::cout << "american locale: " << std::showbase
              << std::put_money(12345678.0)<< '\n';

    std::cout.imbue(std::locale(std::cout.getloc(), new space_out));
    std::cout << "locale with modified moneypunct: "
              << std::put_money(12345678.0)<< '\n';
}

Output:

american locale: $123,456.78
locale with modified moneypunct: 12 34 56 78

See also

provides the character to use as thousands separator
(virtual protected member function)
provides the character to use as decimal point
(virtual protected member function)