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Sprout/sprout/utility/pack.hpp

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/*=============================================================================
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Copyright (c) 2011-2014 Bolero MURAKAMI
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https://github.com/bolero-MURAKAMI/Sprout
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
=============================================================================*/
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#ifndef SPROUT_UTILITY_PACK_HPP
#define SPROUT_UTILITY_PACK_HPP
#include <cstddef>
#include <sprout/config.hpp>
#include <sprout/utility/forward.hpp>
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#include <sprout/type/type_tuple.hpp>
#include <sprout/type_traits/integral_constant.hpp>
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#include <sprout/type_traits/enabler_if.hpp>
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namespace sprout {
//
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// pack_element
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//
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template<std::size_t I, typename... Args>
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struct pack_element
: public std::tuple_element<I, sprout::types::type_tuple<Args...> >
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{};
//
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// pack_element_c
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//
template<std::size_t I, typename T, T... Args>
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struct pack_element_c
: public sprout::pack_element<I, sprout::integral_constant<T, Args>...>::type
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{};
//
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// pack_get
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//
namespace detail {
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template<typename Tup>
struct pack_get_helper;
template<typename... Args>
struct pack_get_helper<sprout::types::type_tuple<Args...> > {
template<typename Head, typename... Tail>
static SPROUT_CONSTEXPR Head&&
eval(Args&&..., Head&& head, Tail&&...) {
return sprout::forward<Head>(head);
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}
};
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} // namespace detail
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template<std::size_t I, typename... Args>
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inline SPROUT_CONSTEXPR typename sprout::pack_element<I, Args&&...>::type
pack_get(Args&&... args) {
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return sprout::detail::pack_get_helper<
typename sprout::types::detail::tuple_take<I, sprout::types::type_tuple<Args...> >::type
>::eval(sprout::forward<Args>(args)...);
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}
} // namespace sprout
#endif // #ifndef SPROUT_UTILITY_PACK_HPP