std::chrono::round(std::chrono::duration) (3) Linux Manual Page

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

See also

                               converts a duration to another, with a different tick interval
duration_cast (function template)
floor(std::chrono::duration) converts a duration to another, rounding down
                               (function template)
(C++17)
ceil(std::chrono::duration) converts a duration to another, rounding up
                               (function template)
(C++17)
round(std::chrono::time_point) converts a time_point to another, rounding to nearest, ties to even
                               (function template)
(C++17)
round
roundf
roundl
lround
lroundf
lroundl
llround
llroundf
llroundl nearest integer, rounding away from zero in halfway cases
                               (function)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)