std::experi...::make_array(3)

💖 NAME 💖

okay so bestie, you've landed on the std::experi...::make_array(3) page in the C++ Standard Libary manual — section 3, and yes the header really spells it “Libary”, we are not fixing it 😭💀. The page name is std::experimental::make_array — std::experimental::make_array (the NAME line said it twice, and honestly? iconic. it ate. 💅).

🌸 Synopsis 🌸

Defined in header <experimental/array>.

template< class D = void, class... Types >
constexpr std::array<VT /* see below */, sizeof...(Types)> make_array( Types&&... t );

The page also tags this as (library fundamentals TS v2). 🎀

Okay so the vibe: it creates a std::array whose size is equal to the number of arguments, and whose elements are initialized from the corresponding arguments. It returns std::array<VT, sizeof...(Types)>{std::forward<Types>(t)...}. Literally main character energy ✨.

If D is void, then the deduced type VT is std::common_type_t<Types...>. Otherwise, it is D.

🚨 If D is void and any of std::decay_t<Types>... is a specialization of std::reference_wrapper, the program is ill-formed. Not cute, not allowed, no cap. 💀

🧚 Notes 🧚

make_array is removed in Library Fundamentals TS v3 because the deduction guide for std::array and std::to_array have been already in C++20. So yeah, it's giving “we have newer toys now” energy, fr fr. 🦋

🛠️ Possible implementation 🛠️

namespace details {
    template<class> struct is_ref_wrapper : std::false_type{};
    template<class T> struct is_ref_wrapper<std::reference_wrapper<T>> : std::true_type{};

    template<class T>
    using not_ref_wrapper = std::negation<is_ref_wrapper<std::decay_t<T>>>;

    template<class D, class...> struct return_type_helper { using type = D; };
    template<class... Types>
    struct return_type_helper<void, Types...> : std::common_type<Types...>
    {
        static_assert(std::conjunction_v<not_ref_wrapper<Types>...>,
                      "Types cannot contain reference_wrappers when D is void");
    };

    template<class D, class... Types>
    using return_type = std::array<typename return_type_helper<D, Types...>::type,
                                   sizeof...(Types)>;
}

template<class D = void, class... Types> constexpr
details::return_type<D, Types...> make_array(Types&&... t) {
    return {std::forward<Types>(t)...}; }

🍓 Example 🍓

// Run this code

#include <experimental/array>
#include <iostream>
#include <type_traits>

int main()
{
    auto arr = std::experimental::make_array(1, 2, 3, 4, 5);
    bool is_array_of_5_ints = std::is_same<decltype(arr),
    std::array<int, 5>>::value;
    std::cout << "Returns an array of five ints? ";
    std::cout << std::boolalpha << is_array_of_5_ints << '\n';
}

👑 Output 👑

Returns an array of five ints? true

🔥 See also 🔥

• C++ documentation for std::array deduction guides — yes, that's a whole thing, iykyk.
• to_array creates a std::array object from a built-in array (function template) — another icon, lowkey.

mwah 💋 source/version/date check: http://cppreference.com, 2024.06.10, footer label std::experi...::make_array(3) — have the day you deserve, bestie 🫶✨