v3/view/counted.hpp

0001 /// \file
0002 // Range v3 library
0003 //
0004 //  Copyright Eric Niebler 2014-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 #ifndef RANGES_V3_VIEW_COUNTED_HPP
0014 #define RANGES_V3_VIEW_COUNTED_HPP
0015
0016 #include <utility>
0017
0018 #include <range/v3/range_fwd.hpp>
0019
0020 #include <range/v3/iterator/concepts.hpp>
0021 #include <range/v3/iterator/counted_iterator.hpp>
0022 #include <range/v3/iterator/default_sentinel.hpp>
0023 #include <range/v3/iterator/traits.hpp>
0024 #include <range/v3/utility/static_const.hpp>
0025 #include <range/v3/view/interface.hpp>
0026 #include <range/v3/view/subrange.hpp>
0027
0028 #include <range/v3/detail/prologue.hpp>
0029
0030 namespace ranges
0031 {
0032     /// \addtogroup group-views
0033     /// @{
0034     template<typename I>
0035     struct counted_view : view_interface<counted_view<I>, finite>
0036     {
0037     private:
0038         friend range_access;
0039         I it_;
0040         iter_difference_t<I> n_;
0041
0042     public:
0043         counted_view() = default;
0044         counted_view(I it, iter_difference_t<I> n)
0045           : it_(it)
0046           , n_(n)
0047         {
0048             RANGES_EXPECT(0 <= n_);
0049         }
0050         counted_iterator<I> begin() const
0051         {
0052             return make_counted_iterator(it_, n_);
0053         }
0054         default_sentinel_t end() const
0055         {
0056             return {};
0057         }
0058         auto size() const
0059         {
0060             return static_cast<detail::iter_size_t<I>>(n_);
0061         }
0062     };
0063
0064     template<typename I>
0065     RANGES_INLINE_VAR constexpr bool enable_borrowed_range<counted_view<I>> = true;
0066
0067 #if RANGES_CXX_DEDUCTION_GUIDES >= RANGES_CXX_DEDUCTION_GUIDES_17
0068     template<typename I>
0069     counted_view(I, iter_difference_t<I>)
0070         -> counted_view<I>;
0071 #endif
0072
0073     namespace views
0074     {
0075         struct cpp20_counted_fn
0076         {
0077             template(typename I)(
0078                 requires input_or_output_iterator<I> AND (!random_access_iterator<I>)) //
0079             subrange<counted_iterator<I>, default_sentinel_t> //
0080             operator()(I it, iter_difference_t<I> n) const
0081             {
0082                 return {make_counted_iterator(std::move(it), n), default_sentinel};
0083             }
0084             template(typename I)(
0085                 requires random_access_iterator<I>)
0086             subrange<I> operator()(I it, iter_difference_t<I> n) const
0087             {
0088                 return {it, it + n};
0089             }
0090         };
0091
0092         struct counted_fn
0093         {
0094             template(typename I)(
0095                 requires input_or_output_iterator<I> AND (!random_access_iterator<I>)) //
0096             counted_view<I> operator()(I it, iter_difference_t<I> n) const
0097             {
0098                 return {std::move(it), n};
0099             }
0100             template(typename I)(
0101                 requires random_access_iterator<I>)
0102             subrange<I> operator()(I it, iter_difference_t<I> n) const
0103             {
0104                 return {it, it + n};
0105             }
0106         };
0107
0108         /// \relates counted_fn
0109         /// \ingroup group-views
0110         RANGES_INLINE_VARIABLE(counted_fn, counted)
0111     } // namespace views
0112
0113     namespace cpp20
0114     {
0115         namespace views
0116         {
0117             RANGES_INLINE_VARIABLE(ranges::views::cpp20_counted_fn, counted)
0118         }
0119     } // namespace cpp20
0120     /// @}
0121 } // namespace ranges
0122
0123 #include <range/v3/detail/epilogue.hpp>
0124 #include <range/v3/detail/satisfy_boost_range.hpp>
0125 RANGES_SATISFY_BOOST_RANGE(::ranges::counted_view)
0126
0127 #endif