std :: chrono :: system_clock :: now（）没有自动

Question

I have one little question: How can i write the following code without auto .

auto a = std::chrono::system_clock::now()
/* do something */
auto b = std::chrono::system_clock::now() - a;

Answer 1

看一下文档 。

std::chrono::system_clock::time_point a = std::chrono::system_clock::now();

Answer 2

std::chrono::time_point<std::chrono::system_clock> a = std::chrono::system_clock::now();

/* do something */

std::chrono::time_point<std::chrono::system_clock> b = std::chrono::system_clock::now() - a;