std::experimental:: make_array

Creates a std::array whose size is equal to the number of arguments and whose elements are initialized from the corresponding arguments. Returns std:: array < VT, sizeof... ( Types ) > { std:: forward < Types > ( t ) ... }.

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.

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.

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

#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';
}

Returns an array of five ints? true

See also