//Original from https://gist.github.com/lichray/6034753
#include <array>
//#include <functional>
template <typename... T>
using common_type_t = typename std::common_type<T...>::type;
template <typename T>
using remove_cv_t = typename std::remove_cv<T>::type;
template <bool, typename T, typename... U>
struct lazy_conditional_c;
template <typename T>
struct lazy_conditional_c<true, T>
{
using type = typename T::type;
};
template <typename T, typename U>
struct lazy_conditional_c<true, T, U>
{
using type = typename T::type;
};
template <typename T, typename U>
struct lazy_conditional_c<false, T, U>
{
using type = typename U::type;
};
template <typename V, typename T, typename... U>
using If = lazy_conditional_c<V::value, T, U...>;
template <typename V, typename T, typename... U>
using If_t = typename If<V, T, U...>::type;
template <typename T>
struct identity_of
{
using type = T;
};
template <template <typename> class F, typename... T>
struct no_type : std::true_type {};
template <template <typename> class F, typename T1, typename... T2>
struct no_type<F, T1, T2...> :
std::integral_constant
<
bool,
not F<T1>::value and no_type<F, T2...>::value
>
{};
template <template <typename> class F, template <typename> class G>
struct composed
{
template <typename T>
using call = F<typename G<T>::type>;
};
template <typename T>
struct _is_reference_wrapper : std::false_type {};
template <typename T>
struct _is_reference_wrapper<std::reference_wrapper<T>> : std::true_type {};
template <typename T>
using is_reference_wrapper =
composed<_is_reference_wrapper, std::remove_cv>::call<T>;
template <typename... T>
constexpr auto make_array(T&&... t)
-> std::array
<
If_t
<
no_type
<
composed
<
is_reference_wrapper,
std::remove_reference
>
::call,
T...
>,
std::common_type<T...>
>,
sizeof...(T)
>
{
return {{ std::forward<T>(t)... }};
}
template <typename V, typename... T>
constexpr auto make_array(T&&... t)
-> std::array
<
V,
sizeof...(T)
>
{
return {{ std::forward<T>(t)... }};
}
template <size_t... I>
struct _indices {};
template <size_t N, size_t... I>
struct _build_indices : _build_indices<N - 1, N - 1, I...> {};
template <size_t... I>
struct _build_indices<0, I...> : _indices<I...> {};
template <typename T, size_t N, size_t... I>
constexpr auto _to_array(T (&arr)[N], _indices<I...>)
-> std::array<remove_cv_t<T>, N>
{
return {{ arr[I]... }};
}
template <typename T, size_t N>
constexpr auto to_array(T (&arr)[N])
-> std::array<remove_cv_t<T>, N>
{
return _to_array(arr, _build_indices<N>());
}
/*
#include <iostream>
int main()
{
auto ch = 'a';
auto const d = 65l;
auto a1 = make_array(ch, d, 0);
static_assert(std::is_same<decltype(a1)::value_type, long>(), "");
std::cout << a1[0] << std::endl;
constexpr auto a2 = to_array("abc");
static_assert(std::is_same<decltype(a2)::value_type, char>(), "");
std::cout << a2.data() << std::endl;
auto a3 = make_array("aa", "bb");
static_assert(std::is_same<decltype(a3)::value_type, char const*>(),
"fix your library");
std::cout << a3[0] << std::endl;
auto a4 = make_array<long>(2, 3U);
static_assert(std::is_same<decltype(a4)::value_type, long>(), "");
std::cout << a4[0] << std::endl;
auto a5 = make_array<short>();
static_assert(std::is_same<decltype(a5)::value_type, short>(), "");
std::cout << a5.size() << std::endl;
int a, b;
auto a6 = make_array<std::reference_wrapper<int>>(a, b);
std::cout << a6.size() << std::endl;
// ** do not compile **
//auto a4 = make_array(std::cref(""));
// ** hard error **
//char s[2][6] = { "nice", "thing" };
//auto a3 = to_array(s);
}
*/
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