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