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

Defined in header <chrono> 
template <class ToDuration, class Rep, class Period>
constexpr ToDuration floor(const 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 an instance of std::chrono::duration.

Parameters

d - duration to convert

Return value

d rounded down to a duration of type ToDuration.

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>{}>>
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

See also

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)
nearest integer not greater than the given value
(function)

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http://en.cppreference.com/w/cpp/chrono/duration/floor