ceph/src/boost/boost/hana/ordering.hpp

   1 /*!
   2 @file
   3 Defines `boost::hana::ordering`.
   4
   5 @copyright Louis Dionne 2013-2017
   6 Distributed under the Boost Software License, Version 1.0.
   7 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
   8  */
   9
  10 #ifndef BOOST_HANA_ORDERING_HPP
  11 #define BOOST_HANA_ORDERING_HPP
  12
  13 #include <boost/hana/fwd/ordering.hpp>
  14
  15 #include <boost/hana/config.hpp>
  16 #include <boost/hana/detail/decay.hpp>
  17 #include <boost/hana/less.hpp>
  18
  19
  20 BOOST_HANA_NAMESPACE_BEGIN
  21     namespace detail {
  22         template <typename F>
  23         struct less_by {
  24             F f;
  25
  26             template <typename X, typename Y>
  27             constexpr decltype(auto) operator()(X&& x, Y&& y) const&
  28             { return hana::less(f(static_cast<X&&>(x)), f(static_cast<Y&&>(y))); }
  29
  30             template <typename X, typename Y>
  31             constexpr decltype(auto) operator()(X&& x, Y&& y) &
  32             { return hana::less(f(static_cast<X&&>(x)), f(static_cast<Y&&>(y))); }
  33         };
  34     }
  35
  36     //! @cond
  37     template <typename F>
  38     constexpr auto ordering_t::operator()(F&& f) const {
  39         return detail::less_by<typename detail::decay<F>::type>{static_cast<F&&>(f)};
  40     }
  41     //! @endcond
  42 BOOST_HANA_NAMESPACE_END
  43
  44 #endif // !BOOST_HANA_ORDERING_HPP