ceph/src/boost/boost/hana/fwd/negate.hpp

   1 /*!
   2 @file
   3 Forward declares `boost::hana::negate`.
   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_FWD_NEGATE_HPP
  11 #define BOOST_HANA_FWD_NEGATE_HPP
  12
  13 #include <boost/hana/config.hpp>
  14 #include <boost/hana/core/when.hpp>
  15
  16
  17 namespace boost { namespace hana {
  18     //! Return the inverse of an element of a group.
  19     //! @ingroup group-Group
  20     //!
  21     //!
  22     //! Example
  23     //! -------
  24     //! @include example/negate.cpp
  25 #ifdef BOOST_HANA_DOXYGEN_INVOKED
  26     constexpr auto negate = [](auto&& x) -> decltype(auto) {
  27         return tag-dispatched;
  28     };
  29 #else
  30     template <typename G, typename = void>
  31     struct negate_impl : negate_impl<G, when<true>> { };
  32
  33     struct negate_t {
  34         template <typename X>
  35         constexpr decltype(auto) operator()(X&& x) const;
  36     };
  37
  38     BOOST_HANA_INLINE_VARIABLE constexpr negate_t negate{};
  39 #endif
  40 }} // end namespace boost::hana
  41
  42 #endif // !BOOST_HANA_FWD_NEGATE_HPP