Re: elapsed time 0 with std::cin

Here's my code:

#include <ctime>
#include <iostream>
#include <string>

class Timer
{
clock_t start_, nticks_;

public:
Timer() : nticks_(0) { start(); }
~Timer() {}

void start() { start_ = clock(); }
void stop() { nticks_ = clock() - start_; }
double elapsed() const { return double(nticks_) / CLOCKS_PER_SEC; }
};

int main()
{
std::string answer;
Timer T;
// for (int n=0; n<100000000; ++n);
std::cout << "? ";
std::cin >> answer;
T.stop();
std::cout << "time elapsed: " << T.elapsed() << "\n";
}

If I use the loop at the commented line, instead of
std::cin, the timer works as expected. I can't figure out
what's wrong here.