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

   1 /*!
   2 @file
   3 Adapts `boost::fusion::list` 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_LIST_HPP
  11 #define BOOST_HANA_EXT_BOOST_FUSION_LIST_HPP
  12
  13 #include <boost/hana/config.hpp>
  14 #include <boost/hana/core/when.hpp>
  15 #include <boost/hana/ext/boost/fusion/detail/common.hpp>
  16 #include <boost/hana/fwd/at.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/fwd/length.hpp>
  21
  22 #include <boost/fusion/algorithm/transformation/pop_front.hpp>
  23 #include <boost/fusion/container/generation/make_list.hpp>
  24 #include <boost/fusion/container/list.hpp>
  25 #include <boost/fusion/container/list/convert.hpp>
  26 #include <boost/fusion/support/tag_of.hpp>
  27 #include <boost/version.hpp>
  28
  29 #include <cstddef>
  30 #include <type_traits>
  31 #include <utility>
  32
  33
  34 #ifdef BOOST_HANA_DOXYGEN_INVOKED
  35 namespace boost { namespace fusion {
  36     //! @ingroup group-ext-fusion
  37     //! Adapter for Boost.Fusion lists.
  38     //!
  39     //!
  40     //! Modeled concepts
  41     //! ----------------
  42     //! A Fusion list is a model of the `Sequence` concept, and all the
  43     //! concepts it refines. That makes it essentially the same as a Hana
  44     //! tuple, although the complexity of some operations might differ from
  45     //! that of a tuple.
  46     //!
  47     //! @include example/ext/boost/fusion/list.cpp
  48     template <typename ...T>
  49     struct list { };
  50 }}
  51 #endif
  52
  53
  54 BOOST_HANA_NAMESPACE_BEGIN
  55     namespace ext { namespace boost { namespace fusion {
  56         struct list_tag;
  57     }}}
  58
  59     template <typename T>
  60     struct tag_of<T, when<
  61         std::is_same<
  62             typename ::boost::fusion::traits::tag_of<T>::type,
  63             ::boost::fusion::traits::tag_of<
  64                 ::boost::fusion::list<>
  65             >::type
  66         >::value
  67     >> {
  68         using type = ext::boost::fusion::list_tag;
  69     };
  70
  71     namespace detail {
  72         template <>
  73         struct is_fusion_sequence<ext::boost::fusion::list_tag> {
  74             static constexpr bool value = true;
  75         };
  76     }
  77
  78     //////////////////////////////////////////////////////////////////////////
  79     // Iterable (the rest is in detail/common.hpp)
  80     //////////////////////////////////////////////////////////////////////////
  81     template <>
  82     struct drop_front_impl<ext::boost::fusion::list_tag> {
  83         template <std::size_t n, typename Xs, std::size_t ...i>
  84         static constexpr auto drop_front_helper(Xs&& xs, std::index_sequence<i...>) {
  85             return hana::make<ext::boost::fusion::list_tag>(
  86                 hana::at_c<n + i>(static_cast<Xs&&>(xs))...
  87             );
  88         }
  89
  90         template <typename Xs, typename N>
  91         static constexpr auto apply(Xs&& xs, N const&) {
  92             constexpr std::size_t n = N::value;
  93             constexpr std::size_t len = decltype(hana::length(xs))::value;
  94             return drop_front_helper<n>(static_cast<Xs&&>(xs),
  95                     std::make_index_sequence<(n < len ? len - n : 0)>{});
  96         }
  97     };
  98
  99     //////////////////////////////////////////////////////////////////////////
 100     // Sequence
 101     //////////////////////////////////////////////////////////////////////////
 102     template <>
 103     struct make_impl<ext::boost::fusion::list_tag> {
 104         template <typename ...Xs>
 105         static constexpr auto apply(Xs&& ...xs) {
 106             return ::boost::fusion::make_list(static_cast<Xs&&>(xs)...);
 107         }
 108     };
 109 BOOST_HANA_NAMESPACE_END
 110
 111 #endif // !BOOST_HANA_EXT_BOOST_FUSION_LIST_HPP