45 lines
1.2 KiB
C++
45 lines
1.2 KiB
C++
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/*!
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@file
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Defines `boost::hana::ordering`.
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@copyright Louis Dionne 2013-2016
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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_ORDERING_HPP
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#define BOOST_HANA_ORDERING_HPP
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#include <boost/hana/fwd/ordering.hpp>
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#include <boost/hana/config.hpp>
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#include <boost/hana/detail/decay.hpp>
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#include <boost/hana/less.hpp>
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BOOST_HANA_NAMESPACE_BEGIN
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namespace detail {
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template <typename F>
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struct less_by {
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F f;
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template <typename X, typename Y>
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constexpr decltype(auto) operator()(X&& x, Y&& y) const&
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{ return hana::less(f(static_cast<X&&>(x)), f(static_cast<Y&&>(y))); }
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template <typename X, typename Y>
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constexpr decltype(auto) operator()(X&& x, Y&& y) &
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{ return hana::less(f(static_cast<X&&>(x)), f(static_cast<Y&&>(y))); }
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};
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}
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//! @cond
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template <typename F>
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constexpr auto ordering_t::operator()(F&& f) const {
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return detail::less_by<typename detail::decay<F>::type>{static_cast<F&&>(f)};
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}
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//! @endcond
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_ORDERING_HPP
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