ceph/src/boost/libs/hana/include/boost/hana/greater.hpp

   1 /*!
   2 @file
   3 Defines `boost::hana::greater`.
   4
   5 @copyright Louis Dionne 2013-2016
   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_GREATER_HPP
  11 #define BOOST_HANA_GREATER_HPP
  12
  13 #include <boost/hana/fwd/greater.hpp>
  14
  15 #include <boost/hana/concept/orderable.hpp>
  16 #include <boost/hana/config.hpp>
  17 #include <boost/hana/core/common.hpp>
  18 #include <boost/hana/core/to.hpp>
  19 #include <boost/hana/core/dispatch.hpp>
  20 #include <boost/hana/detail/concepts.hpp>
  21 #include <boost/hana/detail/has_common_embedding.hpp>
  22 #include <boost/hana/detail/nested_than.hpp> // required by fwd decl
  23 #include <boost/hana/if.hpp>
  24
  25
  26 BOOST_HANA_NAMESPACE_BEGIN
  27     //! @cond
  28     template <typename X, typename Y>
  29     constexpr decltype(auto) greater_t::operator()(X&& x, Y&& y) const {
  30         using T = typename hana::tag_of<X>::type;
  31         using U = typename hana::tag_of<Y>::type;
  32         using Greater = BOOST_HANA_DISPATCH_IF(decltype(greater_impl<T, U>{}),
  33             hana::Orderable<T>::value &&
  34             hana::Orderable<U>::value
  35         );
  36
  37     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
  38         static_assert(hana::Orderable<T>::value,
  39         "hana::greater(x, y) requires 'x' to be Orderable");
  40
  41         static_assert(hana::Orderable<U>::value,
  42         "hana::greater(x, y) requires 'y' to be Orderable");
  43     #endif
  44
  45         return Greater::apply(static_cast<X&&>(x), static_cast<Y&&>(y));
  46     }
  47     //! @endcond
  48     template <typename T, typename U, bool condition>
  49     struct greater_impl<T, U, when<condition>> : default_ {
  50         template <typename X, typename Y>
  51         static constexpr decltype(auto) apply(X&& x, Y&& y) {
  52             return hana::less(static_cast<Y&&>(y),
  53                               static_cast<X&&>(x));
  54         }
  55     };
  56
  57     // Cross-type overload
  58     template <typename T, typename U>
  59     struct greater_impl<T, U, when<
  60         detail::has_nontrivial_common_embedding<Orderable, T, U>::value
  61     >> {
  62         using C = typename hana::common<T, U>::type;
  63         template <typename X, typename Y>
  64         static constexpr decltype(auto) apply(X&& x, Y&& y) {
  65             return hana::greater(hana::to<C>(static_cast<X&&>(x)),
  66                                  hana::to<C>(static_cast<Y&&>(y)));
  67         }
  68     };
  69 BOOST_HANA_NAMESPACE_END
  70
  71 #endif // !BOOST_HANA_GREATER_HPP