std::experimental::make_array

 

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Library fundamentals v2

experimental::propagate_const

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Defined in header <experimental/array>
template< class D = void, class... Types > constexpr std::array<VT /* see below */, sizeof...(Types)> make_array( Types&&... t );		(library fundamentals TS v2)

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

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
to_array	creates a std::array object from a built-in array (function template)