ceph/src/boost/libs/hana/include/boost/hana/ext/boost/fusion/deque.hpp

   1 /*!
   2 @file
   3 Adapts `boost::fusion::deque` 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_BOOST_FUSION_DEQUE_HPP
  11 #define BOOST_HANA_EXT_BOOST_FUSION_DEQUE_HPP
  12
  13 #include <boost/hana/at.hpp>
  14 #include <boost/hana/core/when.hpp>
  15 #include <boost/hana/config.hpp>
  16 #include <boost/hana/ext/boost/fusion/detail/common.hpp>
  17 #include <boost/hana/fwd/core/make.hpp>
  18 #include <boost/hana/fwd/core/tag_of.hpp>
  19 #include <boost/hana/fwd/drop_front.hpp>
  20 #include <boost/hana/length.hpp>
  21
  22 #include <boost/fusion/container/deque.hpp>
  23 #include <boost/fusion/container/generation/make_deque.hpp>
  24 #include <boost/fusion/support/tag_of.hpp>
  25
  26 #include <cstddef>
  27 #include <type_traits>
  28 #include <utility>
  29
  30
  31 #ifdef BOOST_HANA_DOXYGEN_INVOKED
  32 namespace boost { namespace fusion {
  33     //! @ingroup group-ext-fusion
  34     //! Adapter for Boost.Fusion deques.
  35     //!
  36     //!
  37     //! Modeled concepts
  38     //! ----------------
  39     //! A Fusion deque is a model of the `Sequence` concept, and all the
  40     //! concepts it refines. That makes it essentially the same as a Hana
  41     //! tuple, although the complexity of some operations might differ from
  42     //! that of a tuple.
  43     //!
  44     //! @include example/ext/boost/fusion/deque.cpp
  45     template <typename ...T>
  46     struct deque { };
  47 }}
  48 #endif
  49
  50
  51 BOOST_HANA_NAMESPACE_BEGIN
  52     namespace ext { namespace boost { namespace fusion {
  53         struct deque_tag;
  54     }}}
  55
  56     template <typename T>
  57     struct tag_of<T, when<
  58         std::is_same<
  59             typename ::boost::fusion::traits::tag_of<T>::type,
  60             ::boost::fusion::traits::tag_of<
  61                 ::boost::fusion::deque<>
  62             >::type
  63         >::value
  64     >> {
  65         using type = ext::boost::fusion::deque_tag;
  66     };
  67
  68     namespace detail {
  69         template <>
  70         struct is_fusion_sequence<ext::boost::fusion::deque_tag> {
  71             static constexpr bool value = true;
  72         };
  73     }
  74
  75     //////////////////////////////////////////////////////////////////////////
  76     // Iterable (the rest is in detail/common.hpp)
  77     //////////////////////////////////////////////////////////////////////////
  78     template <>
  79     struct drop_front_impl<ext::boost::fusion::deque_tag> {
  80         template <std::size_t n, typename Xs, std::size_t ...i>
  81         static constexpr auto drop_front_helper(Xs&& xs, std::index_sequence<i...>) {
  82             return hana::make<ext::boost::fusion::deque_tag>(
  83                 hana::at_c<n + i>(static_cast<Xs&&>(xs))...
  84             );
  85         }
  86
  87         template <typename Xs, typename N>
  88         static constexpr auto apply(Xs&& xs, N const&) {
  89             constexpr std::size_t n = N::value;
  90             constexpr std::size_t len = decltype(hana::length(xs))::value;
  91             return drop_front_helper<n>(static_cast<Xs&&>(xs),
  92                     std::make_index_sequence<(n < len ? len - n : 0)>{});
  93         }
  94     };
  95
  96     //////////////////////////////////////////////////////////////////////////
  97     // Sequence
  98     //////////////////////////////////////////////////////////////////////////
  99     template <>
 100     struct make_impl<ext::boost::fusion::deque_tag> {
 101         template <typename ...Xs>
 102         static constexpr auto apply(Xs&& ...xs) {
 103             return ::boost::fusion::make_deque(static_cast<Xs&&>(xs)...);
 104         }
 105     };
 106 BOOST_HANA_NAMESPACE_END
 107
 108 #endif // !BOOST_HANA_EXT_BOOST_FUSION_DEQUE_HPP