The following code example is taken from the book
The C++ Standard Library - A Tutorial and Reference
by Nicolai M. Josuttis, Addison-Wesley, 1999
© Copyright Nicolai M. Josuttis 1999
#include <locale>
#include <iostream>
#include <cstdlib>
#include <iterator>
int main()
{
// create copy of current global locale
std::locale loc;
// iterator to read from standard input
typedef std::istreambuf_iterator<char> InIt;
InIt beg = InIt(std::cin);
InIt end = InIt();
// stream which defines input format
std::ios_base& fmt = std::cin;
// declare output arguments
std::ios_base::iostate err;
float value;
// get numeric input facet of the locale loc
std::num_get<char, InIt> const& ng
= std::use_facet<std::num_get<char, InIt> >(loc);
// read value with numeric input facet
ng.get(beg, end, fmt, err, value);
// print value or error message
if (err == std::ios_base::goodbit) {
std::cout << "value: " << value << '\n';
}
else if (err == std::ios_base::eofbit) {
std::cout << "value: " << value << " (EOF encountered)\n";
}
else if (err & std::ios_base::badbit) {
std::cerr << "fatal error while reading numeric value\n";
return EXIT_FAILURE;
}
else if (err & std::ios_base::failbit) {
std::cerr << "format error while reading numeric value\n";
return EXIT_FAILURE;
}
}