#include <iostream>
#include <string>
#include <boost/format.hpp>
 
std::string GetDateFormatString(const std::string& langCode)
{
    if (
       0 == langCode.compare(0, 2, "en")
       || 0 == langCode.compare(0, 2, "EN")
       )
    {
        return std::string("%1$i/%2$i/%3$i");
    }
    else if (
       0 == langCode.compare(0, 2, "fr")
       || 0 == langCode.compare(0, 2, "FR")
       )
    {
        return std::string("%2$i/%1$i/%3$i");
    }
    else if (
       0 == langCode.compare(0, 2, "ja")
       || 0 == langCode.compare(0, 2, "JA")
       || 0 == langCode.compare(0, 2, "jp")
       || 0 == langCode.compare(0, 2, "JP")
       )
    {
        return std::string("%3$i/%2$i/%1$i");
    }
    return std::string("%1$i/%2$i/%3$i");
}

std::string GetDateStringBoost(
    const std::string &langCode, int month, int day, int year)
{
    std::string fmt = GetDateFormatString(langCode);
    std::string ret = boost::str(boost::format(fmt) % month % day % year);
    return ret;
}

int main()
{
    std::cout << GetDateStringBoost("en", 11, 7, 2018) << "\n";
    return 0;
}