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

   1 /*!
   2 @file
   3 Forward declares `boost::hana::keys`.
   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_KEYS_HPP
  11 #define BOOST_HANA_FWD_KEYS_HPP
  12
  13 #include <boost/hana/config.hpp>
  14 #include <boost/hana/core/when.hpp>
  15
  16
  17 BOOST_HANA_NAMESPACE_BEGIN
  18     // Note: This function is documented per datatype/concept only.
  19     //! @cond
  20     template <typename T, typename = void>
  21     struct keys_impl : keys_impl<T, when<true>> { };
  22     //! @endcond
  23
  24     struct keys_t {
  25         template <typename Map>
  26         constexpr auto operator()(Map&& map) const;
  27     };
  28
  29     constexpr keys_t keys{};
  30
  31     //! Returns a `Sequence` containing the name of the members of
  32     //! the data structure.
  33     //! @ingroup group-Struct
  34     //!
  35     //! Given a `Struct` object, `keys` returns a `Sequence` containing the
  36     //! name of all the members of the `Struct`, in the same order as they
  37     //! appear in the `accessors` sequence.
  38     //!
  39     //!
  40     //! Example
  41     //! -------
  42     //! @include example/struct/keys.cpp
  43 #ifdef BOOST_HANA_DOXYGEN_INVOKED
  44     constexpr auto keys = [](auto&& object) {
  45         return implementation_defined;
  46     };
  47 #endif
  48 BOOST_HANA_NAMESPACE_END
  49
  50 #endif // !BOOST_HANA_FWD_KEYS_HPP