How to get the precision of high_resolution_clock?

Question

C++11 defines high_resolution_clock and it has the member types period and rep. But I can not figure out how I can get the precision of that clock.

Or, if I may not get to the precision, can I somehow at least get a count in nanoseconds of the minimum representable time duration between ticks? probably using period?

#include <iostream>
#include <chrono>
void printPrec() {
    std::chrono::high_resolution_clock::rep x = 1;
    // this is not the correct way to initialize 'period':
    //high_resolution_clock::period y = 1;

    std::cout << "The smallest period is "
              << /* what to do with 'x' or 'y' here? */
              << " nanos\n";
}

Answer 1

The minimum representable duration is high_resolution_clock::period::num / high_resolution_clock::period::den seconds. You can print it like this:

std::cout << (double) std::chrono::high_resolution_clock::period::num
             / std::chrono::high_resolution_clock::period::den;

Why is this? A clock's ::period member is defined as "The tick period of the clock in seconds." It is a specialization of std::ratio which is a template to represent ratios at compile-time. It provides two integral constants: num and den, the numerator and denominator of a fraction, respectively.