NAME¶

std::experimental::make_array - std::experimental::make_array

Synopsis¶

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

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¶

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