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std::experimental::make_array

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Experimental
Filesystem library (filesystem TS)
Library fundamentals (library fundamentals TS)
Library fundamentals 2 (library fundamentals TS v2)
Library fundamentals 3 (library fundamentals TS v3)
Extensions for parallelism (parallelism TS)
Extensions for parallelism 2 (parallelism TS v2)
Extensions for concurrency (concurrency TS)
Extensions for concurrency 2 (concurrency TS v2)
Concepts (concepts TS)
Ranges (ranges TS)
Reflection (reflection TS)
Mathematical special functions (special functions TR)
 
 
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.

[edit] 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.

[edit] 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)...};
}

[edit] 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

[edit] See also

C++ documentation for std::array deduction guides
creates a std::array object from a built-in array
(function template) [edit]
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