ceph/src/boost/libs/hana/include/boost/hana/ext/std/pair.hpp

   1 /*!
   2 @file
   3 Adapts `std::pair` for use with Hana.
   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_EXT_STD_PAIR_HPP
  11 #define BOOST_HANA_EXT_STD_PAIR_HPP
  12
  13 #include <boost/hana/config.hpp>
  14 #include <boost/hana/fwd/core/make.hpp>
  15 #include <boost/hana/fwd/core/tag_of.hpp>
  16 #include <boost/hana/fwd/first.hpp>
  17 #include <boost/hana/fwd/second.hpp>
  18
  19 #include <utility>
  20
  21
  22 #ifdef BOOST_HANA_DOXYGEN_INVOKED
  23 namespace std {
  24     //! @ingroup group-ext-std
  25     //! Adaptation of `std::pair` for Hana.
  26     //!
  27     //!
  28     //! Modeled concepts
  29     //! ----------------
  30     //! A `std::pair` models exactly the same concepts as a `hana::pair`.
  31     //! Please refer to the documentation of `hana::pair` for details.
  32     //!
  33     //! @include example/ext/std/pair.cpp
  34     template <typename First, typename Second>
  35     struct pair { };
  36 }
  37 #endif
  38
  39
  40 BOOST_HANA_NAMESPACE_BEGIN
  41     namespace ext { namespace std { struct pair_tag; }}
  42
  43     template <typename First, typename Second>
  44     struct tag_of<std::pair<First, Second>> {
  45         using type = ext::std::pair_tag;
  46     };
  47
  48     //////////////////////////////////////////////////////////////////////////
  49     // Product
  50     //////////////////////////////////////////////////////////////////////////
  51     template <>
  52     struct make_impl<ext::std::pair_tag> {
  53         template <typename X, typename Y>
  54         static constexpr decltype(auto) apply(X&& x, Y&& y) {
  55             return std::make_pair(static_cast<X&&>(x),
  56                                   static_cast<Y&&>(y));
  57         }
  58     };
  59
  60     template <>
  61     struct first_impl<ext::std::pair_tag> {
  62         template <typename T, typename U>
  63         static constexpr T const& apply(std::pair<T, U> const& p)
  64         {  return p.first; }
  65
  66         template <typename T, typename U>
  67         static constexpr T& apply(std::pair<T, U>& p)
  68         {  return p.first; }
  69
  70         template <typename T, typename U>
  71         static constexpr T&& apply(std::pair<T, U>&& p)
  72         {  return static_cast<T&&>(p.first); }
  73     };
  74
  75     template <>
  76     struct second_impl<ext::std::pair_tag> {
  77         template <typename T, typename U>
  78         static constexpr U const& apply(std::pair<T, U> const& p)
  79         {  return p.second; }
  80
  81         template <typename T, typename U>
  82         static constexpr U& apply(std::pair<T, U>& p)
  83         {  return p.second; }
  84
  85         template <typename T, typename U>
  86         static constexpr U&& apply(std::pair<T, U>&& p)
  87         {  return static_cast<U&&>(p.second); }
  88     };
  89 BOOST_HANA_NAMESPACE_END
  90
  91 #endif // !BOOST_HANA_EXT_STD_PAIR_HPP