41 lines
1.1 KiB
C++
41 lines
1.1 KiB
C++
/*!
|
|
@file
|
|
Defines `boost::hana::detail::variadic::at`.
|
|
|
|
@copyright Louis Dionne 2013-2016
|
|
Distributed under the Boost Software License, Version 1.0.
|
|
(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
|
|
*/
|
|
|
|
#ifndef BOOST_HANA_DETAIL_VARIADIC_AT_HPP
|
|
#define BOOST_HANA_DETAIL_VARIADIC_AT_HPP
|
|
|
|
#include <boost/hana/config.hpp>
|
|
|
|
#include <cstddef>
|
|
#include <utility>
|
|
|
|
|
|
BOOST_HANA_NAMESPACE_BEGIN namespace detail { namespace variadic {
|
|
template <std::size_t n, typename = std::make_index_sequence<n>>
|
|
struct at_type;
|
|
|
|
template <std::size_t n, std::size_t ...ignore>
|
|
struct at_type<n, std::index_sequence<ignore...>> {
|
|
private:
|
|
template <typename Nth>
|
|
static constexpr auto go(decltype(ignore, (void*)0)..., Nth nth, ...)
|
|
{ return nth; }
|
|
|
|
public:
|
|
template <typename ...Xs>
|
|
constexpr auto operator()(Xs ...xs) const
|
|
{ return *go(&xs...); }
|
|
};
|
|
|
|
template <std::size_t n>
|
|
constexpr at_type<n> at{};
|
|
}} BOOST_HANA_NAMESPACE_END
|
|
|
|
#endif // !BOOST_HANA_DETAIL_VARIADIC_AT_HPP
|