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

   1 /*!
   2 @file
   3 Forward declares `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_FWD_GREATER_HPP
  11 #define BOOST_HANA_FWD_GREATER_HPP
  12
  13 #include <boost/hana/config.hpp>
  14 #include <boost/hana/core/when.hpp>
  15 #include <boost/hana/detail/nested_than_fwd.hpp>
  16
  17
  18 BOOST_HANA_NAMESPACE_BEGIN
  19     //! Returns a `Logical` representing whether `x` is greater than `y`.
  20     //! @ingroup group-Orderable
  21     //!
  22     //!
  23     //! Signature
  24     //! ---------
  25     //! Given a Logical `Bool` and two Orderables `A` and `B` with a common
  26     //! embedding, the signature is
  27     //! @f$ \mathrm{greater} : A \times B \to Bool @f$.
  28     //!
  29     //! @param x, y
  30     //! Two objects to compare.
  31     //!
  32     //!
  33     //! Example
  34     //! -------
  35     //! @include example/greater.cpp
  36 #ifdef BOOST_HANA_DOXYGEN_INVOKED
  37     constexpr auto greater = [](auto&& x, auto&& y) -> decltype(auto) {
  38         return tag-dispatched;
  39     };
  40 #else
  41     template <typename T, typename U, typename = void>
  42     struct greater_impl : greater_impl<T, U, when<true>> { };
  43
  44     struct greater_t : detail::nested_than<greater_t> {
  45         template <typename X, typename Y>
  46         constexpr decltype(auto) operator()(X&& x, Y&& y) const;
  47     };
  48
  49     constexpr greater_t greater{};
  50 #endif
  51 BOOST_HANA_NAMESPACE_END
  52
  53 #endif // !BOOST_HANA_FWD_GREATER_HPP