48 lines
1.3 KiB
C++
48 lines
1.3 KiB
C++
/*!
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@file
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Defines `boost::hana::detail::variadic::drop_into`.
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@copyright Louis Dionne 2013-2017
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_HANA_DETAIL_VARIADIC_DROP_INTO_HPP
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#define BOOST_HANA_DETAIL_VARIADIC_DROP_INTO_HPP
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#include <boost/hana/config.hpp>
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#include <cstddef>
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#include <utility>
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namespace boost { namespace hana { namespace detail { namespace variadic {
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template <std::size_t n, typename F, typename = std::make_index_sequence<n>>
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struct dropper;
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template <std::size_t n, typename F, std::size_t ...ignore>
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struct dropper<n, F, std::index_sequence<ignore...>> {
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F f;
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template <typename ...Rest>
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constexpr auto go(decltype(ignore, (void*)0)..., Rest ...rest) const
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{ return f(*rest...); }
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template <typename ...Xs>
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constexpr auto operator()(Xs ...xs) const
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{ return go(&xs...); }
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};
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template <std::size_t n>
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struct make_dropper {
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template <typename F>
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constexpr auto operator()(F f) const
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{ return dropper<n, decltype(f)>{f}; }
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};
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template <std::size_t n>
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BOOST_HANA_INLINE_VARIABLE constexpr make_dropper<n> drop_into{};
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}} }} // end namespace boost::hana
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#endif // !BOOST_HANA_DETAIL_VARIADIC_DROP_INTO_HPP
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