c++ sleep_for

来源：https://en.cppreference.com/w/cpp/thread/sleep_for

std::this_thread::sleep_for

#include <chrono>
#include <iostream>
#include <thread>

int main()
{
    using namespace std::chrono_literals;

    std::cout << "Hello waiter\n" << std::flush;

    const auto start = std::chrono::high_resolution_clock::now();
    //std::this_thread::sleep_for(2000ms);
    std::this_thread::sleep_for(std::chrono::milliseconds(2000));
    const auto end = std::chrono::high_resolution_clock::now();
    const std::chrono::duration<double, std::milli> elapsed = end - start;

    std::cout << "Waited " << elapsed << '\n';
}

std::chrono::duration

来源：https://en.cppreference.com/w/cpp/chrono/duration

#include <chrono>
#include <iostream>

using namespace std::chrono_literals;

template<typename T1, typename T2>
using mul = std::ratio_multiply<T1, T2>;

int main()
{
    using microfortnights = std::chrono::duration<float,
        mul<mul<std::ratio<2>, std::chrono::weeks::period>, std::micro>>;
    using nanocenturies = std::chrono::duration<float,
        mul<mul<std::hecto, std::chrono::years::period>, std::nano>>;
    using fps_24 = std::chrono::duration<double, std::ratio<1, 24>>;

    std::cout << "1 second is:\n";

    // integer scale conversion with no precision loss: no cast
    std::cout << std::chrono::milliseconds(1s).count() << " milliseconds\n"
              << std::chrono::microseconds(1s).count() << " microseconds\n"
              << std::chrono::nanoseconds(1s).count() << " nanoseconds\n";

    // integer scale conversion with precision loss: requires a cast
    std::cout << std::chrono::duration_cast<std::chrono::minutes>(1s).count()
              << " minutes\n";

    // floating-point scale conversion: no cast
    std::cout << microfortnights(1s).count() << " microfortnights\n"
              << nanocenturies(1s).count() << " nanocenturies\n"
              << fps_24(1s).count() << " frames at 24fps\n";
}