text: /// \file
  // Range v3 library
  //
  //  Copyright Eric Niebler 2013-present
  //
  //  Use, modification and distribution is subject to the
  //  Boost Software License, Version 1.0. (See accompanying
  //  file LICENSE_1_0.txt or copy at
  //  http://www.boost.org/LICENSE_1_0.txt)
  //
  // Project home: https://github.com/ericniebler/range-v3
  //
  
  #ifndef RANGES_V3_VIEW_CONST_HPP
  #define RANGES_V3_VIEW_CONST_HPP
  
  #include <type_traits>
  #include <utility>
  
  #include <range/v3/range_fwd.hpp>
  
  #include <range/v3/range/access.hpp>
  #include <range/v3/range/concepts.hpp>
  #include <range/v3/range/primitives.hpp>
  #include <range/v3/utility/common_type.hpp>
  #include <range/v3/utility/move.hpp>
  #include <range/v3/utility/static_const.hpp>
  #include <range/v3/view/adaptor.hpp>
  #include <range/v3/view/all.hpp>
  #include <range/v3/view/view.hpp>
  
  #include <range/v3/detail/disable_warnings.hpp>
  
  namespace ranges
  {
      /// \addtogroup group-views
      /// @{
      template<typename Rng>
      struct const_view : view_adaptor<const_view<Rng>, Rng>
      {
      private:
          friend range_access;
          template<bool Const>
          struct adaptor : adaptor_base
          {
              using CRng = meta::const_if_c<Const, Rng>;
              using value_ = range_value_t<CRng>;
              using reference_ =
                  common_reference_t<value_ const &&, range_reference_t<CRng>>;
              using rvalue_reference_ =
                  common_reference_t<value_ const &&, range_rvalue_reference_t<CRng>>;
              adaptor() = default;
              CPP_template(bool Other)(       //
                  requires Const && (!Other)) //
                  constexpr adaptor(adaptor<Other>)
              {}
              reference_ read(iterator_t<CRng> const & it) const
              {
                  return *it;
              }
              rvalue_reference_ iter_move(iterator_t<CRng> const & it) const
                  noexcept(noexcept(rvalue_reference_(ranges::iter_move(it))))
              {
                  return ranges::iter_move(it);
              }
          };
          adaptor<simple_view<Rng>()> begin_adaptor()
          {
              return {};
          }
          CPP_member
          auto begin_adaptor() const -> CPP_ret(adaptor<true>)( //
              requires range<Rng const>)
          {
              return {};
          }
          adaptor<simple_view<Rng>()> end_adaptor()
          {
              return {};
          }
          CPP_member
          auto end_adaptor() const -> CPP_ret(adaptor<true>)( //
              requires range<Rng const>)
          {
              return {};
          }
  
      public:
          const_view() = default;
          explicit const_view(Rng rng)
            : const_view::view_adaptor{std::move(rng)}
          {}
          CPP_member
          constexpr auto CPP_fun(size)()(requires sized_range<Rng>)
          {
              return ranges::size(this->base());
          }
          CPP_member
          constexpr auto CPP_fun(size)()(const requires sized_range<Rng const>)
          {
              return ranges::size(this->base());
          }
      };
  
  #if RANGES_CXX_DEDUCTION_GUIDES >= RANGES_CXX_DEDUCTION_GUIDES_17
      template<typename Rng>
      const_view(Rng &&)->const_view<views::all_t<Rng>>;
  #endif
  
      namespace views
      {
          struct const_fn
          {
              template<typename Rng>
              auto operator()(Rng && rng) const -> CPP_ret(const_view<all_t<Rng>>)( //
                  requires viewable_range<Rng> && input_range<Rng>)
              {
                  return const_view<all_t<Rng>>{all(static_cast<Rng &&>(rng))};
              }
          };
  
          /// \relates const_fn
          /// \ingroup group-views
          RANGES_INLINE_VARIABLE(view_closure<const_fn>, const_)
      } // namespace views
      /// @}
  } // namespace ranges
  
  #include <range/v3/detail/reenable_warnings.hpp>
  #include <range/v3/detail/satisfy_boost_range.hpp>
  RANGES_SATISFY_BOOST_RANGE(::ranges::const_view)
  
  #endif
  