function that's (implicitly) applied here is The function that's (implicitly) applied here is std::make_tuple std::make_tuple.. fmapN :: (a -> b -> ...) -> f a -> f b -> ... template [{a1, b1}, {a1, b2}, {a2, b1}, {a2, b2}] -- now replacing make_tuple with f -- => [[c11], [c12], [c21], [c22]] 84IN CASE IT ESCAPED YOUR NOTICE… IN CASE IT ESCAPED constexpr auto cartesian_product(Ts &&...ts) { if constexpr (sizeof...(Ts) == 0) { return std::make_tuple(std::tuple{}); } else { return [](First &&first, Rest &&

std::pair myPair( std::piecewise_construct, std::make_tuple("abc", 3), std::make_tuple(100, '*') ); We’ll also see a couple of useful idioms with std::tie. 22 Construct foo() { std::tuple t = std::make_tuple(1, 2, 3); return std::make_pair(42, false); } 58 C++17 CTAD alert! Function templates make_pair and make_tuple will deduce their argument types implicitly create a tuple of references in at least three ways: int a=1, b=2; auto ab1 = std::make_tuple(std::ref(a), std::ref(b)); auto ab2 = std::tie(a, b); auto ab3 = std::forward_as_tuple(a

(b == 0) { return std::make_tuple( std::make_error_code(std::errc::invalid_argument), 0); } auto const result = a / b; return std::make_tuple(std::error_code{}, result); } (b == 0) { return std::make_tuple( std::make_error_code(std::errc::invalid_argument), 0); } auto const result = a / b; return std::make_tuple(std::error_code{}, result); } (b == 0) { return std::make_tuple( std::make_error_code(std::errc::invalid_argument), 0); } auto const result = a / b; return std::make_tuple(std::error_code{}, result); }

#include #include std::tuple f() { return std::make_tuple(1, 2.3, "456"); } int main() { auto [x, y, z] = f(); std::cout << x << ", " << y << ", " << can be saved. Basic Operations There are three core functions for the use of tuples: 1. std::make_tuple: construct tuple 2. std::get: Get the value of a position in the tuple 3. std::tie: tuple unpacking get_student(int id) { if (id == 0) return std::make_tuple(3.8, 'A', "John"); if (id == 1) return std::make_tuple(2.9, 'C', "Jack"); if (id == 2) return std::make_tuple(1.7, 'D', "Ive"); 54 4.3 Tuples CHAPTER

std::to_string(i); }) ; 1 2 3 4 5 6 7 8 auto r = comp | async::sync_wait(); 9 auto [str] = r.value_or(std::make_tuple(""_s)); 10 23Composition auto comp = s1.schedule() | async::then([] { return 42; }) | std::to_string(i); }) ; 1 2 3 4 5 6 7 8 auto r = comp | async::sync_wait(); 9 auto [str] = r.value_or(std::make_tuple(""_s)); 10 auto r = comp | async::sync_wait(); auto comp = 1 s1.schedule() 2 | async::then([] async::then([] (int i) { return std::to_string(i); }) 5 6 ; 7 8 9 auto [str] = r.value_or(std::make_tuple(""_s)); 10 23.1Composition auto comp = s1.schedule() | async::then([] { return 42; })

#include #include std::tuple f() { return std::make_tuple(1, 2.3, "456"); } int main() { auto [x, y, z] = f(); std::cout << x << ", " << y << ", " << 定义结构）。但 std::pair 的缺陷是 49 4.3 元组 第 4 章容器 显而易见的，只能保存两个元素。 元组基本操作 关于元组的使用有三个核心的函数： 1. std::make_tuple: 构造元组 2. std::get: 获得元组某个位置的值 3. std::tie: 元组拆包 #include #include auto == 0) return std::make_tuple(3.8, ’A’, " 张三"); if (id == 1) return std::make_tuple(2.9, ’C’, " 李四"); if (id == 2) return std::make_tuple(1.7, ’D’, " 王五"); return std::make_tuple(0.0, ’D’, "null");

gine& engine, const QString& fileName, const QString& viewName) { ./... return std::make_tuple(std::move(context), std::move(component), viewName); } 58Don’t forget about transform_error

becomes:Cppcon 2023 | Rud Merriam | A Journey into Non-Virtual Polymorphism 32 auto tup = std::make_tuple( DigitalPin{1, false}, DigitalPin{2, true}, AnalogPin{3, 42}, SerialPort{5}); auto&

:ranges::forward_: adjacency_list Graph = stdi:vectormake_tuple(size_tfy) ，Pr' auto make_property_graph(const V& vertices，const Ek edges，bool dj EE 人 昌 Aero