std::chrono::floor(std::chrono::duration)

 

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std::chrono::duration

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

Returns the greatest duration t representable in ToDuration that is less or equal to d.

The function does not participate in the overload resolution unless ToDuration is a specialization of std::chrono::duration.

Parameters

d

-

duration to convert

Return value

d rounded down to a duration of type ToDuration.

Possible implementation

namespace detail { template<class> inline constexpr bool is_duration_v = false; template<class Rep, class Period> inline constexpr bool is_duration_v< std::chrono::duration<Rep, Period>> = true; }   template <class To, class Rep, class Period, class = std::enable_if_t<detail::is_duration_v<To>>> constexpr To floor(const duration<Rep, Period>& d) { To t = std::chrono::duration_cast<To>(d); if (t > d) return t - To{1}; return t; }

Example

Run this code

#include <iostream>
#include <iomanip>
#include <chrono>
 
int main()
{
    using namespace std::chrono_literals;
    using Sec = std::chrono::seconds;
    for (std::cout << "Duration\tFloor\tRound\tCeil\n"
                      "(ms)\t\t(sec)\t(sec)\t(sec)\n";
        auto const d: {
            +4999ms, +5000ms, +5001ms, +5499ms, +5500ms, +5999ms,
            -4999ms, -5000ms, -5001ms, -5499ms, -5500ms, -5999ms, }) {
        std::cout << std::showpos << d.count() << "\t\t"
                  << std::chrono::floor<Sec>(d).count() << '\t'
                  << std::chrono::round<Sec>(d).count() << '\t'
                  << std::chrono::ceil <Sec>(d).count() << '\n';
    }
}

Output:

Duration   Floor   Round   Ceil
(ms)       (sec)   (sec)   (sec)
+4999      +4      +5      +5
+5000      +5      +5      +5
+5001      +5      +5      +6
+5499      +5      +5      +6
+5500      +5      +6      +6
+5999      +5      +6      +6
-4999      -5      -5      -4
-5000      -5      -5      -5
-5001      -6      -5      -5
-5499      -6      -5      -5
-5500      -6      -6      -5
-5999      -6      -6      -5

See also

duration_cast (C++11)	converts a duration to another, with a different tick interval (function template)
ceil(std::chrono::duration) (C++17)	converts a duration to another, rounding up (function template)
round(std::chrono::duration) (C++17)	converts a duration to another, rounding to nearest, ties to even (function template)
floor(std::chrono::time_point) (C++17)	converts a time_point to another, rounding down (function template)
floorfloorffloorl (C++11)(C++11)	nearest integer not greater than the given value (function)