将 sys_seconds 设置为纪元，即零

Question

我正在努力寻找将 sys_seconds 重置为零的好方法

date::sys_seconds st;
//st = date::sys_seconds(0);            //no matching conversion for functional-style cast from 'int' to 'date::sys_seconds'
//st = date::sys_seconds{date::sys_seconds(0)}; //no matching conversion for functional-style cast from 'int' to 'date::sys_seconds'
//st = std::chrono::system_clock::from_time_t(0);   //no viable overloaded '='
//st = date::sys_seconds(std::chrono::system_clock::from_time_t(0));    //no matching conversion for functional-style cast 
st = std::chrono::time_point_cast<std::chrono::seconds>(std::chrono::system_clock::from_time_t(0)); //works, but verbose

有没有更好的方法？

Answer 1

st = {};

说明：sys_seconds 的默认构造函数将事物设置为零。所以这只是默认构造一个sys_seconds并将其赋值给st。其他方法包括：

st = date::sys_seconds{};

和：

using namespace std::chrono_literals;
st = date::sys_seconds{0s};

将 sys_seconds 设置为纪元，即零

Set sys_seconds to the epoch i.e. zero

c++

date

chrono