ceph/src/boost/boost/hana/ext/boost/fusion/vector.hpp

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