C++: What is std::views::chunk_by (C++23)?

1#include <ranges>
2
3std::vector<int> v = {1, 1, 2, 2, 2, 3, 1, 1};
4
5// Chunk by equality
6auto chunks = v | std::views::chunk_by(std::ranges::equal_to{});
7for (auto chunk : chunks) {
8    for (int x : chunk) {
9        std::cout << x << " ";
10    }
11    std::cout << "| ";
12}
13// Output: 1 1 | 2 2 2 | 3 | 1 1 |
14
15// Chunk by predicate
16std::vector<int> v2 = {1, 3, 5, 2, 4, 6, 7, 9};
17auto chunks2 = v2 | std::views::chunk_by([](int a, int b) {
18    return (a % 2) == (b % 2);  // Same parity
19});
20for (auto chunk : chunks2) {
21    std::cout << "[";
22    for (size_t i = 0; i < chunk.size(); i++) {
23        if (i > 0) std::cout << ", ";
24        std::cout << chunk[i];
25    }
26    std::cout << "] ";
27}
28// Output: [1, 3, 5] [2, 4, 6] [7, 9]
29
30// Lazy evaluation
31auto first_chunk = chunks2 | std::views::take(1);