ClickHouse/libs/libcommon/include/ext/make_array_n.h
2017-06-13 07:14:23 +03:00

44 lines
1.3 KiB
C++

#pragma once
#include <utility>
#include <type_traits>
#include <array>
/** \brief Produces std::array of specified size, containing copies of provided object.
* Copy is performed N-1 times, and the last element is being moved.
* This helper allows to initialize std::array in place.
*/
namespace ext
{
namespace detail
{
template<std::size_t size, typename T, std::size_t... indexes>
constexpr auto make_array_n_impl(T && value, std::index_sequence<indexes...>)
{
/// Comma is used to make N-1 copies of value
return std::array<std::decay_t<T>, size>{ (static_cast<void>(indexes), value)..., std::forward<T>(value) };
}
}
template<typename T>
constexpr auto make_array_n(std::integral_constant<std::size_t, 0>, T &&)
{
return std::array<std::decay_t<T>, 0>{};
}
template<std::size_t size, typename T>
constexpr auto make_array_n(std::integral_constant<std::size_t, size>, T && value)
{
return detail::make_array_n_impl<size>(std::forward<T>(value), std::make_index_sequence<size - 1>{});
}
template<std::size_t size, typename T>
constexpr auto make_array_n(T && value)
{
return make_array_n(std::integral_constant<std::size_t, size>{}, std::forward<T>(value));
}
}