41 lines
1.1 KiB
C++
41 lines
1.1 KiB
C++
/*!
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@file
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Defines `boost::hana::difference`.
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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_DIFFERENCE_HPP
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#define BOOST_HANA_DIFFERENCE_HPP
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#include <boost/hana/fwd/difference.hpp>
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#include <boost/hana/config.hpp>
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#include <boost/hana/core/dispatch.hpp>
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#include <boost/hana/erase_key.hpp>
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namespace boost { namespace hana {
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//! @cond
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template <typename Xs, typename Ys>
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constexpr auto difference_t::operator()(Xs&& xs, Ys&& ys) const {
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using S = typename hana::tag_of<Xs>::type;
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using Difference = BOOST_HANA_DISPATCH_IF(difference_impl<S>,
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true
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);
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return Difference::apply(static_cast<Xs&&>(xs), static_cast<Ys&&>(ys));
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}
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//! @endcond
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template <typename S, bool condition>
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struct difference_impl<S, when<condition>> : default_ {
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template <typename ...Args>
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static constexpr auto apply(Args&& ...) = delete;
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};
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}} // end namespace boost::hana
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#endif // !BOOST_HANA_DIFFERENCE_HPP
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