How C++20 Ranges allow functional, lazy stream processing without temporary vector allocations:

#include <ranges>
#include <vector>
#include <iostream>

std::vector<int> numbers = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

auto results = numbers 
    | std::views::filter([](int n) { return n % 2 == 0; })
    | std::views::transform([](int n) { return n * n; })
    | std::views::take(3);

for (int v : results) {
    std::cout << v << " "; // Prints: 4 16 36
}

std::views are 100% lazy: no intermediate vectors are allocated, and elements are computed on-demand during loop iteration!

The pipeline operator | makes range transformations readable from top-to-bottom instead of nested inside-out function calls.

In C++23, std::ranges::to<std::vector>() makes collecting ranges back into concrete containers trivial!