12 C++20’s <chrono> Calendars and Time Zones in MSVC Miya Natsuhara ("MEE-yuh Not-soo-HAR-uh") Miya.Natsuhara@microsoft.com Software Engineer, Visual C++ LibrariesWelcome to CppCon 2021! Join tracking the issues, PRs, discussions, etc. related to C++20 chrono: Extensions to <chrono> (github.com) • Feature branch (feature/chrono) for rapid development and collaboration • Code Review Videos class types • chrono::day • chrono::month • chrono::year • chrono::month_day • chrono::weekday • chrono::weekday_indexed • chrono::year_month_day • chrono::year_month_day_last • chrono::year_month_weekday_last

Agenda  Compile-Time Rational Numbers  Durations  Clocks  Time Points  Dates  Time Zones <chrono> 4 Agenda  Compile-Time Rational Numbers  Durations  Clocks  Time Points  Dates rational numbers at compile time  Always normalized representation  Needed for durations in the <chrono> library6 Compile-Time Rational Numbers  Define a rational number: using r1 = ratio<1, 60>; Time Zones10 Durations  Interval between two points in time  Represented by std::duration from <chrono>, contains:  A tick  A tick period = seconds between 2 ticks = rational constant  template

温馨提示： 1. 会用到第二讲（ RAII 与智能指针）里的知识 2. 课件中一部分代码是基于 C++17 的 个人认为， C++11 中很多特性， 其实可以看做是为了支持多线程而 顺带引入的……如 chrono 、移动 、 lambda 、 RAII…… 第 0 章：时间 C 语言如何处理时间： time.h • long t0 = time(NULL); // 获取从 1970 年 1 月 std::chrono • 利用 C++ 强类型的特点，明确区分时间点与时间段，明确区分不同的时间单位。 • 时间点例子： 2022 年 1 月 8 日 13 点 07 分 10 秒 • 时间段例子： 1 分 30 秒 • 时间点类型： chrono::steady_clock::time_point 等 • 时间段类型： chrono::milliseconds ， chrono::seconds chrono::seconds ， chrono::minutes 等 • 方便的运算符重载：时间点 + 时间段 = 时间点，时间点 - 时间点 = 时间段 • auto t0 = chrono::steady_clock::now(); // 获取当前时间点 • auto t1 = t0 + chrono::seconds(30);

Calendars & Timezones  <chrono> is extended to support calendars and timezones  Only Gregorian calendar is supported  Custom calendars can be added and can interoperate with <chrono>59 Calendars & Timezones certain duration  Additionally:  using sys_seconds = sys_timechrono::seconds>;  using sys_days = sys_timechrono::days>;  Example: system_clock::time_point t { sys_days { 2020y

visualizers (.natvis) ☑️�Just My Code debugging Demo C++20 in action Thu, Oct 28 – 10:30am C++20’s <chrono> Calendars and Time Zones in MSVC Miya Natsuhara – `Online _4 Tue, Oct 26 – 10:30am Documentation Studio: 64-bit IDE, C++20, WSL 2, and more – Sy Brand & Marian Luparu Thursday 28th • C++20’s <chrono> Calendars and Time Zones in MSVC – Miya Natsuhara • An Editor Can Do That? Debugging Assembly

java 进军数据处理，高性能计算等领域 。 java 第八帝国 cpp 第十一共和国 chrono 和 complex 也定义了一些 literials std::literials 内部定义一览 std::literials::string_literials std::literials::chrono_literials 字符串 <--> 数字 第 4 章 java 经典操作：字符串

Studio: 64-bit IDE, C++20, WSL 2, and more – Sy Brand & Marian Luparu Thursday 28th • C++20’s <chrono> Calendars and Time Zones in MSVC – Miya Natsuhara • An Editor Can Do That? Debugging Assembly

Features • Available  Investigating  Reviewing PR  Done • Maintainer Priorities • Large features: Chrono, Format, Spaceship43 Wiki • Changelog • Infeasible: Look at commit history between releases •