Docs4dev
Docs
cpp / latest / chrono / duration / floor.html

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

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

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

Output:

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

See also

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

© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
https://en.cppreference.com/w/cpp/chrono/duration/floor