{"id":5870,"date":"2020-03-27T08:10:41","date_gmt":"2020-03-27T08:10:41","guid":{"rendered":"https:\/\/www.modernescpp.com\/index.php\/c-20-coroutines-more-details\/"},"modified":"2023-09-28T07:45:21","modified_gmt":"2023-09-28T07:45:21","slug":"c-20-coroutines-more-details","status":"publish","type":"post","link":"https:\/\/www.modernescpp.com\/index.php\/c-20-coroutines-more-details\/","title":{"rendered":"C++20: More Details to Coroutines"},"content":{"rendered":"

After I gave you in my last post (C++20: Coroutines – A First Overview<\/a>) my first impression of coroutines, I want to provide more details today.\u00a0Once more, we get in C++20 not coroutines but a framework for building coroutines.<\/p>\n

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My job in this and further posts is to explain the framework for building coroutines. Ultimately, you can create your own or use an existing implementation of coroutines such as the excellent one\u00a0cppcoro<\/a>\u00a0from Lewis Baker.<\/p>\n

Today’s post is in-between: This post is not an overview but also not an in-depth dive into the coroutines framework that follows in the next posts.<\/p>\n

The first question you may have is: When should I use coroutines?<\/p>\n

Typical Use-Cases<\/h2>\n

Coroutines are the usual way to write event-driven applications<\/a>. The event-driven application can\u00a0be simulations, games, servers, user interfaces, or algorithms. For example, I wrote a a few years ago a defibrillator simulator in Python. This simulator helped us, in particular, to make clinical usability studies. A defibrillator is an event-driven application, and I implemented it, consequentially, based on the event-driven Python framework twisted<\/a>.<\/p>\n

Coroutines are also typically used for\u00a0cooperative multitasking. The key to cooperative multitasking is that each task takes as much time\u00a0as it needs. Cooperative multitasking<\/a> stands in contrast to preemptive multitasking, for which a scheduler decides how long each task gets the CPU. Cooperative multitasking often makes concurrency easier because a concurrent job can not be interrupted in a critical region. If you are still puzzled by the terms cooperative and preemptive, I found an excellent overview and read here:\u00a0Cooperative vs. Preemptive: a quest to maximize concurrency power<\/a><\/p>\n

Underlying Ideas<\/span><\/p>\n

Coroutines in C++20 are asymmetric, first-class, and stackless.<\/p>\n