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

int main() {
    std::vector<int> data{1,2,3,4,5,6};
    auto evens = data | std::views::filter([](int x){ return x % 2 == 0; });
    auto count = std::ranges::count_if(evens, [](int){ return true; }); // count elements in view
    std::cout << "evens = " << count << '\n';
}