C++11 Stopwatch

kkloepper_fav.cpp

class Stopwatch {
    using clock = std::chrono::high_resolution_clock;
    bool is_running() const { return stop_time_ == clock::time_point::min(); }
    clock::time_point end_time() const { return is_running() ? clock::now() : stop_time_; }
    clock::time_point begin_time_{clock::now()}, stop_time_{clock::time_point::min()};
public:
    void stop() { if (is_running()) stop_time_ = clock::now(); }
    clock::duration elapsed() const { return end_time() - begin_time_; }
};

std::ostream& operator<<(std::ostream& os, Stopwatch const& stopwatch)
{
   auto e = std::chrono::duration<double, std::micro>(stopwatch.elapsed());
   auto oldLoc = std::cout.imbue(std::locale(""));
   std::cout << e.count() << " microseconds\n";
   std::cout.imbue(oldLoc);
   return os;
}

I think the operator<< implementation should be using "os" (std::ostream) parameter instead of std::cout?