Lesson 44: Ranges Library (C++20)

Ranges Library (C++20)\n\nThe Ranges library unifies algorithms and containers under a common view‑based approach. Views are lazy, composable adapters that transform a range without materialising intermediate containers.\n\n---\n\n## Common views\n- std::views::filter\n- std::views::transform\n- std::views::take\n- std::views::drop\n- std::views::reverse\n\n## Example: Filtering and transforming a vector\ncpp\nstd::vector<int> numbers = {1, 2, 3, 4, 5, 6};\nauto evenSquares = numbers\n | std::views::filter([](int n){ return n % 2 == 0; })\n | std::views::transform([](int n){ return n * n; });\nfor (int v : evenSquares) {\n std::cout << v << ' ';\n}\nstd::cout << '\\n';\n\n\nThe above pipeline never creates a temporary container; each element is processed on‑the‑fly.\n\n## Using std::ranges::sort\ncpp\nstd::vector<std::string> words = {\"apple\", \"banana\", \"cherry\"};\nstd::ranges::sort(words, std::greater{}); // sort descending\nfor (const auto& w : words) std::cout << w << ' ';\nstd::cout << '\\n';\n\n\n> Tip: When an algorithm accepts a range (e.g., std::ranges::find), you can pass a view directly without calling .begin()/.end().\n\n---\n\n<Alert type="warning">Views hold references to the underlying container; ensure the container outlives the view to avoid dangling references.