How to print a double with a comma

Question

In C++ I\'ve got a float/double variable.

When I print this with for example cout the resulting string is period-delimited.

cout << 3.1415 <         


        

Answer 1

Very old thread, but anyway ... I had the problem to fill a text entry under Gtkmm-3.0 with the outcome of a distance calculation. To make things clearer I add an example, where I have concentrated some wisdoms of several posts I read the last days:

#include 
// next not necessary, added only for clarity
#include 
Gtk::Entry m_Text;
// a distance measured in kilometers
double totalDistance = 35.45678;
std::stringstream str;
// I am using locale of Germany, pay attention to the _
str.imbue(std::locale("de_DE"));
// now we have decimal comma instead of point
str << std::fixed << std::setprecision(4) << std::setw(16) << totalDistance << " km";
// the wished formatting corresponds to "%16.4f km" in printf
m_Text.set_text(str.str());