**Course Title:** Modern C++ Programming: Mastering C++ with Best Practices and Advanced Techniques **Section Title:** Advanced C++ Features: C++20 and Beyond **Topic:** Using C++20 ranges for cleaner, more expressive code. ### Introduction C++20 introduces a new feature called "ranges" that allows for cleaner, more expressive code._ranges are a way to describe a sequence of values in a composable, readable, and efficient way.In this topic, we will explore the basics of ranges, how to use them, and some examples that demonstrate their power. ### What are ranges? A range is a sequence of values that can be processed sequentially. It can be a sequence of numbers, characters, or even more complex data structures. Ranges are lazy, meaning that they only compute the values as needed, rather than computing them all upfront. ### Range types There are several types of ranges in C++20: * **Views**: These are ranges that do not own their data. Instead, they reference existing data and provide a way to view it in a different way. * **OWNED Ranges**: These are ranges that own their data. ### Core Concepts The Range Library is composed of a few core concepts: * **Ranges**: Represent a sequence of elements. All you can do is ask a range for its begin and end. * **Views**: Transform a range in some way without forcing evaluation. View's end is determined by the underlying range. * **Adaptors**: Consume a range and return a new one. ### Using ranges ranges are created using the `std::views` namespace. This namespace contains functions that create views that can be composed together to create complex ranges. ```cpp #include <ranges> #include <vector> #include <iostream> int main() { std::vector<int> numbers = {1, 2, 3, 4, 5}; // create a view of the numbers that are even auto even_numbers = numbers | std::views::filter([](int x) { return x % 2 == 0; }); // create a view of the even numbers that are greater than 2 auto even_numbers_greater_than_2 = even_numbers | std::views::filter([](int x) { return x > 2; }); // print the even numbers greater than 2 for (int number : even_numbers_greater_than_2) { std::cout << number << std::endl; } return 0; } ``` ### Converting a range to another data structure You can use the `std::vector` constructor to create a `std::vector` from a range. ```cpp #include <ranges> #include <vector> #include <iostream> int main() { std::vector<int> numbers = {1, 2, 3, 4, 5}; // create a vector of the even numbers greater than 2 std::vector<int> even_numbers_greater_than_2 = numbers | std::views::filter([](int x) { return x % 2 == 0; }) | std::views::filter([](int x) { return x > 2; }); // print the even numbers greater than 2 for (int number : even_numbers_greater_than_2) { std::cout << number << std::endl; } return 0; } ``` ### Benefits of ranges The benefits of ranges include: * **readability**: ranges are much more readable than traditional C++ loops. * **Expressiveness**: ranges can be composed together to create complex data transformations. * **Efficiency**: ranges are lazy, meaning they only compute the values as needed. ### Conclusion ranges are a powerful feature of C++20 that allow for cleaner, more expressive code. By understanding how to use ranges, you can write more readable, maintainable, and efficient code. ### Practical Takeaways * **Use ranges for data transformations**: Instead of using traditional C++ loops, use ranges to create composable data transformations. * **Use views to transform ranges**: Use views to create new ranges that are derived from existing ranges. * **Use adaptors to consume and create new ranges**: Use adaptors to consume existing ranges and create new ones. ### Additional Resources * [cppreference.com: std::ranges](https://en.cppreference.com/w/cpp/ranges) * [cppreference.com: std::views](https://en.cppreference.com/w/cpp/ranges/views) ### Next Topic In the next topic, we will explore another exciting feature of C++20 called "modules" which allows for creating more modular, reusable, and maintainable code. If you have any questions or need further clarification on this topic, please leave a comment below.