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.
d rounded down to a duration of type ToDuration.
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;
}[edit] 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[edit] See also
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