Formatted C++ Output in Monetary Values

The format controls do not insert either the thousands separator or the currency symbol. To do this you need to use locales and the money_put facet. However this is not pretty.

The following code outputs a value in US dollars:

int main()
{
  // Define a locale
  std::locale loc("US");

  // Define the facet
  const std::money_put<char>& output =
    std::use_facet<std::money_put<char> >(loc);

  // Define an iterator to std::cout
  std::ostreambuf_iterator<char, std::char_traits<char> > iterator(std::cout);

  // Use the locale for the output stream
  std::cout.imbue(loc);

  // Ensure that the currency symbol is output
  std::cout.setf(std::ios_base::showbase);

  std::cout << "Value is: ";

  // Output a value to std::cout
  output.put(iterator, false, std::cout, ' ', 12300000.0);
  std::cout << std::endl;
  return 0;
}

If the second parameter to money_put.put is false then the currency symbol is output (e.g. $123,000.00), if set to true then the international monetary sign is used (e.g. USD123,000,00).

The value is interpreted as a value in cents (in general it is the smallest unit of the locale's currency).

However mixing normal values and currency values in the output stream is awkward, imbuing std::cout with a locale affects all subsequent output (which may or may not be what you want). The way round this is to using money_put on a string, and wrap this in a class to make everything easier:

#include <iostream>
#include <iterator>
#include <locale>
#include <string>
#include <sstream>

class MoneyOutputter
{
public:
  MoneyOutputter(const char* const locale_name = "US") : 
      loc(locale_name), 
      output(std::use_facet<std::money_put<char> >(loc)),
      iterator(os)
  {
    os.imbue(loc);
    os.setf(std::ios_base::showbase);
  }

  std::string as_string(double value)
  {
    os.str("");  // clear string
    output.put(iterator, false, os, ' ', value * 100.0);
    return os.str();
  }

private:
  std::locale loc;
  const std::money_put<char>& output;
  std::ostringstream os;
  std::ostreambuf_iterator<char, std::char_traits<char> > iterator;
};

int main()
{
  MoneyOutputter outputter;

  double value1 = 235460.0;
  double value2 = 123000.0;
  double value3 = 4500.0;
  double value4 = 545.0;

  std::cout << "Jones " << value1 << " " << outputter.as_string(value2) << " "
    << outputter.as_string(value3) << " " << outputter.as_string(value4) 
    << std::endl;
  return 0;
}