std::chrono::round(std::chrono::duration) (3) - Linux Manuals

std::chrono::round(std::chrono::duration): std::chrono::round(std::chrono::duration)

NAME

std::chrono::round(std::chrono::duration) - std::chrono::round(std::chrono::duration)

Synopsis

Defined in header <chrono>
template <class ToDuration, class Rep, class Period> (since C++17)
constexpr ToDuration round(const duration<Rep, Period>& d);

Returns the value t representable in ToDuration that is the closest to d. If there are two such values, returns the even value (that is, the value t such that t % 2 == 0).
The function does not participate in the overload resolution unless ToDuration is an instance of std::chrono::duration and std::chrono::treat_as_floating_point<typename ToDuration::rep>::value is false

Parameters

d - duration to convert

Return value

d rounded to the nearest duration of type ToDuration, rounding to even in halfway cases.

Possible implementation

  template <class T> struct is_duration : std::false_type {};
  template <class Rep, class Period> struct is_duration<
      std::chrono::duration<Rep, Period>> : std::true_type {};

  template <class To, class Rep, class Period,
            class = std::enable_if_t<is_duration<To>{} &&
                   !std::chrono::treat_as_floating_point<typename To::rep>{}>>
  constexpr To round(const std::chrono::duration<Rep, Period>& d)
  {
      To t0 = std::chrono::duration::floor<To>(d);
      To t1 = t0 + To{1};
      auto diff0 = d - t0;
      auto diff1 = t1 - d;
      if (diff0 == diff1) {
          if (t0.count() & 1)
              return t1;
          return t0;
      } else if (diff0 < diff1) {
          return t0;
      }
      return t1;
  }

Example

 This section is incomplete
 Reason: no example