v3/view/indirect.hpp

0001 /// \file
0002 // Range v3 library
0003 //
0004 //  Copyright Eric Niebler 2013-present
0005 //
0006 //  Use, modification and distribution is subject to the
0007 //  Boost Software License, Version 1.0. (See accompanying
0008 //  file LICENSE_1_0.txt or copy at
0009 //  http://www.boost.org/LICENSE_1_0.txt)
0010 //
0011 // Project home: https://github.com/ericniebler/range-v3
0012 //
0013
0014 #ifndef RANGES_V3_VIEW_INDIRECT_HPP
0015 #define RANGES_V3_VIEW_INDIRECT_HPP
0016
0017 #include <iterator>
0018 #include <type_traits>
0019 #include <utility>
0020
0021 #include <meta/meta.hpp>
0022
0023 #include <range/v3/range_fwd.hpp>
0024
0025 #include <range/v3/range/access.hpp>
0026 #include <range/v3/range/traits.hpp>
0027 #include <range/v3/utility/move.hpp>
0028 #include <range/v3/utility/static_const.hpp>
0029 #include <range/v3/view/adaptor.hpp>
0030 #include <range/v3/view/view.hpp>
0031
0032 #include <range/v3/detail/prologue.hpp>
0033
0034 namespace ranges
0035 {
0036     /// \addtogroup group-views
0037     /// @{
0038     template<typename Rng>
0039     struct indirect_view : view_adaptor<indirect_view<Rng>, Rng>
0040     {
0041     private:
0042         friend range_access;
0043
0044         template<bool IsConst>
0045         struct adaptor : adaptor_base
0046         {
0047             friend adaptor<!IsConst>;
0048             using CRng = meta::const_if_c<IsConst, Rng>;
0049
0050             adaptor() = default;
0051             template(bool Other)(
0052                 requires IsConst && CPP_NOT(Other)) //
0053             constexpr adaptor(adaptor<Other>) noexcept
0054             {}
0055
0056             // clang-format off
0057             constexpr auto CPP_auto_fun(read)(iterator_t<CRng> const &it)(const)
0058             (
0059                 return **it
0060             )
0061             constexpr auto CPP_auto_fun(iter_move)(iterator_t<CRng> const &it)(const)
0062             (
0063                 return ranges::iter_move(*it)
0064             )
0065             // clang-format on
0066         };
0067
0068         CPP_member
0069         constexpr auto begin_adaptor() noexcept //
0070             -> CPP_ret(adaptor<false>)(
0071                 requires (!simple_view<Rng>()))
0072         {
0073             return {};
0074         }
0075         CPP_member
0076         constexpr auto begin_adaptor() const noexcept //
0077             -> CPP_ret(adaptor<true>)(
0078                 requires range<Rng const>)
0079         {
0080             return {};
0081         }
0082
0083         CPP_member
0084         constexpr auto end_adaptor() noexcept //
0085             -> CPP_ret(adaptor<false>)(
0086                 requires (!simple_view<Rng>()))
0087         {
0088             return {};
0089         }
0090         CPP_member
0091         constexpr auto end_adaptor() const noexcept //
0092             -> CPP_ret(adaptor<true>)(
0093                 requires range<Rng const>)
0094         {
0095             return {};
0096         }
0097
0098     public:
0099         indirect_view() = default;
0100         constexpr explicit indirect_view(Rng rng)
0101           : indirect_view::view_adaptor{detail::move(rng)}
0102         {}
0103         CPP_auto_member
0104         constexpr auto CPP_fun(size)()(const //
0105             requires sized_range<Rng const>)
0106         {
0107             return ranges::size(this->base());
0108         }
0109         CPP_auto_member
0110         constexpr auto CPP_fun(size)()(
0111             requires sized_range<Rng>)
0112         {
0113             return ranges::size(this->base());
0114         }
0115     };
0116
0117     template<typename Rng>
0118     RANGES_INLINE_VAR constexpr bool enable_borrowed_range<indirect_view<Rng>> = //
0119         enable_borrowed_range<Rng>;
0120
0121 #if RANGES_CXX_DEDUCTION_GUIDES >= RANGES_CXX_DEDUCTION_GUIDES_17
0122     template<typename Rng>
0123     indirect_view(Rng &&) //
0124         -> indirect_view<views::all_t<Rng>>;
0125 #endif
0126
0127     namespace views
0128     {
0129         struct indirect_fn
0130         {
0131             template(typename Rng)(
0132                 requires viewable_range<Rng> AND input_range<Rng> AND
0133                 // We shouldn't need to strip references to test if something
0134                 // is readable. https://github.com/ericniebler/stl2/issues/594
0135                 // indirectly_readable<range_reference_t<Rng>>)
0136                 ((bool)indirectly_readable<range_value_t<Rng>>)) // Cast to bool needed
0137                                                                  // for GCC (???))
0138             constexpr auto operator()(Rng && rng) const
0139             {
0140                 return indirect_view<all_t<Rng>>{all(static_cast<Rng &&>(rng))};
0141             }
0142         };
0143
0144         /// \relates indirect_fn
0145         /// \ingroup group-views
0146         RANGES_INLINE_VARIABLE(view_closure<indirect_fn>, indirect)
0147     } // namespace views
0148     /// @}
0149 } // namespace ranges
0150
0151 #include <range/v3/detail/epilogue.hpp>
0152
0153 #include <range/v3/detail/satisfy_boost_range.hpp>
0154 RANGES_SATISFY_BOOST_RANGE(::ranges::indirect_view)
0155
0156 #endif