/*! @file Defines `boost::hana::ordering`. @copyright Louis Dionne 2013-2016 Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) */ #ifndef BOOST_HANA_ORDERING_HPP #define BOOST_HANA_ORDERING_HPP #include <boost/hana/fwd/ordering.hpp> #include <boost/hana/config.hpp> #include <boost/hana/detail/decay.hpp> #include <boost/hana/less.hpp> BOOST_HANA_NAMESPACE_BEGIN namespace detail { template <typename F> struct less_by { F f; template <typename X, typename Y> constexpr decltype(auto) operator()(X&& x, Y&& y) const& { return hana::less(f(static_cast<X&&>(x)), f(static_cast<Y&&>(y))); } template <typename X, typename Y> constexpr decltype(auto) operator()(X&& x, Y&& y) & { return hana::less(f(static_cast<X&&>(x)), f(static_cast<Y&&>(y))); } }; } //! @cond template <typename F> constexpr auto ordering_t::operator()(F&& f) const { return detail::less_by<typename detail::decay<F>::type>{static_cast<F&&>(f)}; } //! @endcond BOOST_HANA_NAMESPACE_END #endif // !BOOST_HANA_ORDERING_HPP