C++: What is std::ranges (C++20)?

1#include <ranges>
2#include <vector>
3
4std::vector<int> nums = {1, 2, 3, 4, 5, 6, 7, 8};
5
6// Traditional
7for (auto n : nums) {
8    if (n % 2 == 0) std::cout << n * 2 << " ";
9}
10
11// Ranges (lazy evaluation)
12auto result = nums
13    | std::views::filter([](int n) { return n % 2 == 0; })
14    | std::views::transform([](int n) { return n * 2; });
15
16for (auto n : result) {
17    std::cout << n << " ";
18}
19
20// Other views
21auto first5 = nums | std::views::take(5);
22auto skip2 = nums | std::views::drop(2);
23auto reversed = nums | std::views::reverse;
24auto chunked = nums | std::views::chunk(3);
25auto zipped = std::views::zip(nums, nums);
26
27// Algorithms with projections
28std::ranges::sort(nums, std::ranges::greater{});