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std::experimental::to_array - cppreference.com

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Merged into ISO C++ The functionality described on this page was merged into the mainline ISO C++ standard as of 7/2019, see std::to_array (since C++20) 
template< class T, std::size_t N >
constexpr std::array<std::remove_cv_t<T>, N> to_array(T (&a)[N]);
(library fundamentals TS v2)

Creates a std::array from the built-in array a. The elements of the std::array are copy-initialized from the corresponding element of a.

Parameters

a - the built-in array to be used to initialize the std::array

Return value

An std::array object whose elements are copy-initialized from the corresponding element of a.

Possible implementation

namespace detail
{
    template<class T, std::size_t N, std::size_t... I>
    constexpr std::array<std::remove_cv_t<T>, N>
        to_array_impl(T (&a)[N], std::index_sequence<I...>)
    {
        return { {a[I]...} };
    }
}

template<class T, std::size_t N>
constexpr std::array<std::remove_cv_t<T>, N> to_array(T (&a)[N])
{
    return detail::to_array_impl(a, std::make_index_sequence<N>{});
}

Example

#include <cassert>
#include <cstdlib>
#include <experimental/array>
#include <unistd.h>

// mkstemp(3) that works
template<std::size_t N>
int tempfd(char const (&tmpl)[N])
{
    auto s = std::experimental::to_array(tmpl);
    int fd = mkstemp(s.data());
    if (fd != -1)
        unlink(s.data());

    return fd;
}

int main()
{
    int fd = tempfd("/tmp/test.XXXXXX");
    int rt = close(fd);
    assert(rt == 0);
}

See also

(library fundamentals TS v2)

 creates a std::array object whose size and optionally element type are deduced from the arguments
(function template) [edit]