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Defined in header <chrono> | ||
template<class ToDuration,class Rep,class Period> constexpr ToDuration round(conststd::chrono::duration<Rep, Period>& d); | (since C++17) | |
Returns the valuet representable inToDuration that is the closest tod. If there are two such values, returns the even value (that is, the valuet such thatt%2==0).
The function does not participate in the overload resolution unlessToDuration is a specialization ofstd::chrono::duration andstd::chrono::treat_as_floating_point_v<typename ToDuration::rep> isfalse.
Contents |
| d | - | duration to convert |
d rounded to the nearest duration of typeToDuration, rounding to even in halfway cases.
namespace detail{template<class>inlineconstexprbool is_duration_v=false;template<class Rep,class Period>inlineconstexprbool 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>&&!std::chrono::treat_as_floating_point_v<typename To::rep>>>constexpr To round(conststd::chrono::duration<Rep, Period>& d){ To t0=std::chrono::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;}elseif(diff0< diff1)return t0;return t1;} |
#include <chrono>#include <iomanip>#include <iostream> int main(){usingnamespace std::chrono_literals;std::cout<<"Duration\tFloor\tRound\tCeil\n";for(using Sec=std::chrono::seconds;autoconst 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:
DurationFloorRoundCeil+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
(C++11) | converts a duration to another, with a different tick interval (function template)[edit] |
(C++17) | converts a duration to another, rounding down (function template)[edit] |
(C++17) | converts a duration to another, rounding up (function template)[edit] |
| converts a time_point to another, rounding to nearest, ties to even (function template)[edit] | |
(C++11)(C++11)(C++11)(C++11)(C++11)(C++11)(C++11)(C++11)(C++11) | nearest integer, rounding away from zero in halfway cases (function)[edit] |
