How to Pass Values Directly to std::span in C++20 скачать в хорошем качестве

How to Pass Values Directly to std::span in C++20

Learn how to effectively pass values directly into `std::span` in C++20 using clear methods and examples. --- This video is based on the question https://stackoverflow.com/q/74960217/ asked by the user 'asmbaty' ( https://stackoverflow.com/u/4910232/ ) and on the answer https://stackoverflow.com/a/74960229/ provided by the user 'HolyBlackCat' ( https://stackoverflow.com/u/2752075/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions. Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: How to pass values directly to std::span? Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l... The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license. If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com. --- Understanding std::span in C++20 std::span is a lightweight, non-owning view into a contiguous sequence of elements, introduced in C++20. It enables functions to operate on data collections without needing copies. Handling collections is vital in programming, and knowing how to effectively pass values is essential for efficient code execution. The Problem You have a function defined as follows: [[See Video to Reveal this Text or Code Snippet]] This function is expected to receive a std::span of integers. However, when you try to pass a list of values directly into the function like this: [[See Video to Reveal this Text or Code Snippet]] You encounter an issue as std::span expects a certain type that cannot accept rvalues directly. Solution: How to Pass Values to std::span To pass values directly to your std::span-receiving function, you can utilize std::array which allows the construction of a temporary array for the span. Here's how you can do it: Using std::array You can create an instance of std::array and pass it to the function as shown below: [[See Video to Reveal this Text or Code Snippet]] Adjusting the span Type Notice that std::span<int> does not accept rvalues directly because it expects a modifiable range. If you are only reading the data (as inferred from the intent behind your function), you should adjust your span type to std::span<const int>. The modified function signature then looks like this: [[See Video to Reveal this Text or Code Snippet]] This change ensures that your function is ready to accept temporarily created arrays or other ranges not intended for modification. Alternative Method There is also an alternative way to make a direct call using initializer lists. The following code works as well: [[See Video to Reveal this Text or Code Snippet]] The outer braces indicate a braced-init-list which helps the compiler recognize the structure as an array. Conclusion In conclusion, passing values directly to std::span in C++20 can be achieved using a few straightforward methods. By either constructing an std::array, adjusting the span type to const, or utilizing braced initialization, you can successfully work around the limitation of passing rvalues directly to the function. This keeps your code efficient and clean while ensuring you maintain the desired functionality. Incorporating these techniques will enable you to leverage std::span effectively, making your code more flexible and easier to maintain.