# include int main() { using namespace biu::literals; for (auto [a, b] : biu::sequence(std::array{2, 2, 2})) std::cout << "{} {}\n"_f(a, b); std::optional> a; auto b = a.value_or(std::vector{1, 2, 3}) | biu::toLvalue | ranges::views::transform([](int i){ return i + 1; }) | ranges::to_vector; }