ceph/src/boost/libs/hana/include/boost/hana/remove_range.hpp

   1 /*!
   2 @file
   3 Defines `boost::hana::remove_range` and `boost::hana::remove_range_c`.
   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_REMOVE_RANGE_HPP
  11 #define BOOST_HANA_REMOVE_RANGE_HPP
  12
  13 #include <boost/hana/fwd/remove_range.hpp>
  14
  15 #include <boost/hana/at.hpp>
  16 #include <boost/hana/concept/integral_constant.hpp>
  17 #include <boost/hana/concept/sequence.hpp>
  18 #include <boost/hana/config.hpp>
  19 #include <boost/hana/core/dispatch.hpp>
  20 #include <boost/hana/core/make.hpp>
  21 #include <boost/hana/integral_constant.hpp>
  22 #include <boost/hana/length.hpp>
  23
  24 #include <cstddef>
  25 #include <utility>
  26
  27
  28 BOOST_HANA_NAMESPACE_BEGIN
  29     //! @cond
  30     template <typename Xs, typename From, typename To>
  31     constexpr auto remove_range_t::operator()(Xs&& xs, From const& from, To const& to) const {
  32         using S = typename hana::tag_of<Xs>::type;
  33         using RemoveRange = BOOST_HANA_DISPATCH_IF(remove_range_impl<S>,
  34             hana::Sequence<S>::value &&
  35             hana::IntegralConstant<From>::value &&
  36             hana::IntegralConstant<To>::value
  37         );
  38
  39     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
  40         static_assert(hana::Sequence<S>::value,
  41         "hana::remove_range(xs, from, to) requires 'xs' to be a Sequence");
  42
  43         static_assert(hana::IntegralConstant<From>::value,
  44         "hana::remove_range(xs, from, to) requires 'from' to be an IntegralConstant");
  45
  46         static_assert(hana::IntegralConstant<To>::value,
  47         "hana::remove_range(xs, from, to) requires 'to' to be an IntegralConstant");
  48     #endif
  49
  50         return RemoveRange::apply(static_cast<Xs&&>(xs), from, to);
  51     }
  52     //! @endcond
  53
  54     template <typename S, bool condition>
  55     struct remove_range_impl<S, when<condition>> : default_ {
  56         template <std::size_t offset, typename Xs, std::size_t ...before, std::size_t ...after>
  57         static constexpr auto
  58         remove_range_helper(Xs&& xs, std::index_sequence<before...>,
  59                                      std::index_sequence<after...>)
  60         {
  61             return hana::make<S>(
  62                 hana::at_c<before>(static_cast<Xs&&>(xs))...,
  63                 hana::at_c<offset + after>(static_cast<Xs&&>(xs))...
  64             );
  65         }
  66
  67         template <typename Xs, typename From, typename To>
  68         static constexpr auto apply(Xs&& xs, From const&, To const&) {
  69             constexpr std::size_t from = From::value;
  70             constexpr std::size_t to = To::value;
  71             constexpr std::size_t len = decltype(hana::length(xs))::value;
  72             constexpr std::size_t before = from == to ? len : from;
  73             constexpr std::size_t after = from == to ? 0 : len - to;
  74
  75             static_assert(from <= to,
  76             "hana::remove_range(xs, from, to) requires '[from, to)' to be a "
  77             "valid interval, meaning that 'from <= to'");
  78             static_assert(from == to || from >= 0,
  79             "hana::remove_range(xs, from, to) requires 'from' to be non-negative");
  80             static_assert(from == to || to <= len,
  81             "hana::remove_range(xs, from, to) requires 'to <= length(xs)'");
  82
  83             return remove_range_helper<to>(static_cast<Xs&&>(xs),
  84                                            std::make_index_sequence<before>{},
  85                                            std::make_index_sequence<after>{});
  86         }
  87     };
  88
  89     template <std::size_t from, std::size_t to>
  90     struct remove_range_c_t {
  91         template <typename Xs>
  92         constexpr decltype(auto) operator()(Xs&& xs) const {
  93             return hana::remove_range(static_cast<Xs&&>(xs),
  94                                       hana::size_c<from>,
  95                                       hana::size_c<to>);
  96         }
  97     };
  98 BOOST_HANA_NAMESPACE_END
  99
 100 #endif // !BOOST_HANA_REMOVE_RANGE_HPP