Print integer with thousands and millions separator

c++, fstream, separator

Solution

`imbue()` the output stream with a locale that has the desired separator. For example:

#include <iostream>
#include <locale>

int main()
{
    // imbue the output stream with a locale.
    int i = 45749785;
    std::cout << i << "\n";

    std::cout.imbue(std::locale(""));
    std::cout << i << "\n";
}

Output on my machine (and online demo):

45749785
45,749,785

As commented, and answered, by James Kanze imbue the input stream also to read the separated `int` values without manually modifying the input.

See Stroustrop's Appendix D: Locales for a detailed overview of locales.

Problem

Got a question about printing Integers with thousands/millions separator. I got a Textfile where i got Country, City,Total Population. I have to read in the File, and sort by country. If country is eual, i have to sort descending by population. Textfile is like: Australia........Sydney.........10.123.456 Brazil...........Sao Paulo.......7.123.345 I read all 3 into a seperated string. Then i erase all "." in the population string. Then i use atoi() to cast the population string to an integer. Now i can sort by population if country is equal. This sort works correctly. So far so good. But i need to get thousand/millions seperator into the printing of the population. If i use string,with the "." for population, sorting dont work correctly. Its sorted like: x........x......1.123456 x........x......10.123.456 x........x......2.123.232 It have to look like: Australia........Sydney.........10.123.456 Australia........Brisbane.......8.123.456 Is there a way to manipulate the printing by adding separator the the int again? Many Thanks in advance

Original source