op_minus.md

operator-

• chrono[meta header]
• std::chrono[meta namespace]
• function template[meta id-type]
• cpp11[meta cpp]

namespace std {
namespace chrono {
  // duration - duration = duration
  template <class Rep1, class Period1, class Rep2, class Period2>
  constexpr typename common_type<duration<Rep1, Period1>, duration<Rep2, Period2>>::type
    operator-(const duration<Rep1, Period1>& lhs,
              const duration<Rep2, Period2>& rhs);      // (1)

  // time_point - duration = time_point
  template <class Clock, class Duration1, class Rep2, class Period2>
  time_point<Clock, typename common_type<Duration1, duration<Rep2, Period2>>::type>
    operator-(const time_point<Clock, Duration1>& lhs,
              const duration<Rep2, Period2>& rhs);      // (2) C++11

  // time_point - duration = time_point
  template <class Clock, class Duration1, class Rep2, class Period2>
  constexpr time_point<Clock, typename common_type<Duration1, duration<Rep2, Period2>>::type>
    operator-(const time_point<Clock, Duration1>& lhs,
              const duration<Rep2, Period2>& rhs);      // (2) C++14

  // time_point - time_point - duration
  template <class Clock, class Duration1, class Duration2>
  typename common_type<Duration1, Duration2>::type
    operator-(const time_point<Clock, Duration1>& lhs,
              const time_point<Clock, Duration2>& rhs); // (3) C++11

  // time_point - time_point - duration
  template <class Clock, class Duration1, class Duration2>
  constexpr typename common_type<Duration1, Duration2>::type
    operator-(const time_point<Clock, Duration1>& lhs,
              const time_point<Clock, Duration2>& rhs); // (3) C++14
}}

• duration[link /reference/chrono/duration.md]
• time_point[link /reference/chrono/time_point.md]
• common_type[link /reference/type_traits/common_type.md]

概要

duration, time_pointの減算を行う

戻り値

• (1)

using cd = common_type<decltype(lhs), decltype(rhs)>;
return cd(cd(lhs).count() - cd(rhs).count());

• common_type[link /reference/type_traits/common_type.md]
• count()[link /reference/chrono/duration/count.md]

• (2)

return lhs + (-rhs);

• (3)

return lhs.time_since_epoch() - rhs.time_since_epoch();

• time_since_epoch[link /reference/chrono/time_point/time_since_epoch.md]

例

#include <iostream>
#include <chrono>

using namespace std::chrono;

int main()
{
  // durationの減算
  {
    seconds s = seconds(3) - seconds(2);
    std::cout << s.count() << std::endl;

    milliseconds ms = seconds(3) - milliseconds(2);
    std::cout << ms.count() << std::endl;
  }
  std::cout << std::endl;

  // time_pointの減算
  {
    time_point<system_clock> now = system_clock::now();

    time_point<system_clock> p1 = now - seconds(3);
    std::cout << p1.time_since_epoch().count() << std::endl;

    seconds s = duration_cast<seconds>(now - p1);
    std::cout << s.count() << std::endl;
  }
}

• seconds[link seconds.md]
• count()[link duration/count.md]
• milliseconds[link milliseconds.md]
• time_point[link time_point.md]
• system_clock[link system_clock.md]
• now()[link system_clock/now.md]
• time_since_epoch()[link time_point/time_since_epoch.md]
• duration_cast[link duration_cast.md]

出力例

1
2998

1314584313008925
3

バージョン

言語

• C++11

処理系

• GCC, C++11 mode: 4.6.1
• Visual C++: 2012, 2013, 2015

参照

• N3469 Constexpr Library Additions: chrono, v3