chunk_by.hpp

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// Range v3 library
//
//  Copyright Hui Xie 2021
//
//  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_CHUNK_BY_HPP
#define RANGES_V3_VIEW_CHUNK_BY_HPP
 
#include <type_traits>
#include <utility>
 
#include <meta/meta.hpp>
 
#include <range/v3/range_fwd.hpp>
 
#include <range/v3/algorithm/adjacent_find.hpp>
#include <range/v3/functional/bind_back.hpp>
#include <range/v3/functional/not_fn.hpp>
#include <range/v3/iterator/default_sentinel.hpp>
#include <range/v3/range/access.hpp>
#include <range/v3/range/concepts.hpp>
#include <range/v3/range/traits.hpp>
#include <range/v3/utility/optional.hpp>
#include <range/v3/utility/semiregular_box.hpp>
#include <range/v3/utility/static_const.hpp>
#include <range/v3/view/all.hpp>
#include <range/v3/view/facade.hpp>
#include <range/v3/view/subrange.hpp>
#include <range/v3/view/view.hpp>
 
#include <range/v3/detail/prologue.hpp>
 
namespace ranges
{

    template<typename Rng, typename Fun>
    struct chunk_by_view
      : view_facade<chunk_by_view<Rng, Fun>,
                    is_finite<Rng>::value ? finite : range_cardinality<Rng>::value>
    {
    private:
        friend range_access;
        Rng rng_;
        // cached version of the end of the first subrange / start of the second subrange
        detail::non_propagating_cache<iterator_t<Rng>> second_;
        semiregular_box_t<Fun> fun_;
 
        struct cursor
        {
        private:
            friend range_access;
            friend chunk_by_view;
            iterator_t<Rng> cur_;
            iterator_t<Rng> next_cur_;
            sentinel_t<Rng> last_;
            semiregular_box_ref_or_val_t<Fun, false> fun_;
 
#ifdef _MSC_VER
            template<typename I = iterator_t<Rng>>
            subrange<I> read() const
            {
                return {cur_, next_cur_};
            }
#else
            subrange<iterator_t<Rng>> read() const
            {
                return {cur_, next_cur_};
            }
#endif
            void next()
            {
                cur_ = next_cur_;
                auto partition_cur = adjacent_find(cur_, last_, not_fn(fun_));
                next_cur_ =
                    partition_cur != last_ ? ranges::next(partition_cur) : partition_cur;
            }
 
            bool equal(default_sentinel_t) const
            {
                return cur_ == last_;
            }
            bool equal(cursor const & that) const
            {
                return cur_ == that.cur_;
            }
            cursor(semiregular_box_ref_or_val_t<Fun, false> fun, iterator_t<Rng> first,
                   iterator_t<Rng> next_cur, sentinel_t<Rng> last)
              : cur_(first)
              , next_cur_(next_cur)
              , last_(last)
              , fun_(fun)
            {}
 
        public:
            cursor() = default;
        };
        cursor begin_cursor()
        {
            auto first = ranges::begin(rng_);
            auto last = ranges::end(rng_);
            if(!second_)
            {
                auto partition_cur = adjacent_find(first, last, not_fn(fun_));
                second_ =
                    partition_cur != last ? ranges::next(partition_cur) : partition_cur;
            }
            return {fun_, first, *second_, last};
        }
 
    public:
        chunk_by_view() = default;
        constexpr chunk_by_view(Rng rng, Fun fun)
          : rng_(std::move(rng))
          , fun_(std::move(fun))
        {}
    };
 
#if RANGES_CXX_DEDUCTION_GUIDES >= RANGES_CXX_DEDUCTION_GUIDES_17
    template(typename Rng, typename Fun)(
        requires copy_constructible<Fun>) chunk_by_view(Rng &&, Fun)
        ->chunk_by_view<views::all_t<Rng>, Fun>;
#endif
 
    namespace views
    {
        struct chunk_by_base_fn
        {
            template(typename Rng, typename Fun)(
                requires viewable_range<Rng> AND forward_range<Rng> AND //
                    indirect_relation<Fun, iterator_t<Rng>>)            //
            constexpr chunk_by_view<all_t<Rng>, Fun>
            operator()(Rng && rng, Fun fun) const
            {
                return {all(static_cast<Rng &&>(rng)), std::move(fun)};
            }
        };
 
        struct chunk_by_fn : chunk_by_base_fn
        {
            using chunk_by_base_fn::operator();
 
            template<typename Fun>
            constexpr auto operator()(Fun fun) const
            {
                return make_view_closure(bind_back(chunk_by_base_fn{}, std::move(fun)));
            }
        };

        RANGES_INLINE_VARIABLE(chunk_by_fn, chunk_by)
    } // namespace views
} // namespace ranges
 
#include <range/v3/detail/epilogue.hpp>
#include <range/v3/detail/satisfy_boost_range.hpp>
RANGES_SATISFY_BOOST_RANGE(::ranges::chunk_by_view)
 
#endif