/// \file
// Range v3 library
//
//  Copyright Eric Niebler 2013-present
//  Copyright Tomislav Ivek 2015-2016
//
//  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_SET_ALGORITHM_HPP
#define RANGES_V3_VIEW_SET_ALGORITHM_HPP

#include <utility>
#include <iterator>
#include <algorithm>
#include <functional>
#include <type_traits>
#include <meta/meta.hpp>
#include <range/v3/range_fwd.hpp>
#include <range/v3/range/access.hpp>
#include <range/v3/range/traits.hpp>
#include <range/v3/range/primitives.hpp>
#include <range/v3/view/facade.hpp>
#include <range/v3/functional/comparisons.hpp>
#include <range/v3/functional/identity.hpp>
#include <range/v3/functional/invoke.hpp>
#include <range/v3/iterator/default_sentinel.hpp>
#include <range/v3/utility/move.hpp>
#include <range/v3/utility/semiregular.hpp>
#include <range/v3/utility/static_const.hpp>
#include <range/v3/view/all.hpp>
#include <range/v3/view/view.hpp>

namespace ranges
{
    /// \cond
    namespace detail
    {
        template<typename Rng1, typename Rng2, typename C, typename P1, typename P2,
                 template<bool, typename...> class Cursor, cardinality Cardinality>
        struct set_algorithm_view
          : view_facade<
                set_algorithm_view<Rng1, Rng2, C, P1, P2, Cursor, Cardinality>,
                Cardinality>
        {
        private:
            friend range_access;
            semiregular_t<C> pred_;
            semiregular_t<P1> proj1_;
            semiregular_t<P2> proj2_;
            Rng1 rng1_;
            Rng2 rng2_;

            template<bool IsConst>
            using cursor = Cursor<IsConst, Rng1, Rng2, C, P1, P2>;

            cursor<simple_view<Rng1>() && simple_view<Rng2>()> begin_cursor()
            {
                return {pred_, proj1_, proj2_,
                        ranges::begin(rng1_), ranges::end(rng1_),
                        ranges::begin(rng2_), ranges::end(rng2_)};
            }
            CPP_member
            auto begin_cursor() const -> CPP_ret(cursor<true>)(
                requires Range<Rng1 const> && Range<Rng2 const>)
            {
                return {pred_, proj1_, proj2_,
                        ranges::begin(rng1_), ranges::end(rng1_),
                        ranges::begin(rng2_), ranges::end(rng2_)};
            }
        public:
            set_algorithm_view() = default;
            set_algorithm_view(Rng1 rng1, Rng2 rng2, C pred, P1 proj1, P2 proj2)
              : pred_(std::move(pred))
              , proj1_(std::move(proj1))
              , proj2_(std::move(proj2))
              , rng1_(std::move(rng1))
              , rng2_(std::move(rng2))
            {}
        };

        template<bool IsConst, typename Rng1, typename Rng2, typename C, typename P1,
            typename P2>
        struct set_difference_cursor
        {
        private:
            friend struct set_difference_cursor<!IsConst, Rng1, Rng2, C, P1, P2>;
            using pred_ref_ = semiregular_ref_or_val_t<C, IsConst>;
            using proj1_ref_ = semiregular_ref_or_val_t<P1, IsConst>;
            using proj2_ref_ = semiregular_ref_or_val_t<P2, IsConst>;
            pred_ref_ pred_;
            proj1_ref_ proj1_;
            proj2_ref_ proj2_;

            template<typename T>
            using constify_if = meta::const_if_c<IsConst, T>;

            using R1 = constify_if<Rng1>;
            using R2 = constify_if<Rng2>;

            iterator_t<R1> it1_;
            sentinel_t<R1> end1_;

            iterator_t<R2> it2_;
            sentinel_t<R2> end2_;

            void satisfy()
            {
                while(it1_ != end1_)
                {
                    if(it2_ == end2_)
                        return;

                    if(invoke(pred_, invoke(proj1_, *it1_), invoke(proj2_, *it2_)))
                        return;

                    if(!invoke(pred_, invoke(proj2_, *it2_), invoke(proj1_, *it1_)))
                        ++it1_;

                    ++it2_;
                }
            }

        public:
            using value_type = range_value_t<constify_if<Rng1>>;
            using single_pass = meta::or_c<SinglePass<iterator_t<R1>>,
                                           SinglePass<iterator_t<R2>>>;

            set_difference_cursor() = default;
            set_difference_cursor(pred_ref_ pred, proj1_ref_ proj1, proj2_ref_ proj2,
                                  iterator_t<R1> it1, sentinel_t<R1> end1,
                                  iterator_t<R2> it2, sentinel_t<R2> end2)
              : pred_(std::move(pred)), proj1_(std::move(proj1)), proj2_(std::move(proj2)),
                it1_(std::move(it1)), end1_(std::move(end1)), it2_(std::move(it2)), end2_(std::move(end2))
            {
                satisfy();
            }
            CPP_template(bool Other)(
                requires IsConst && (!Other))
            set_difference_cursor(set_difference_cursor<Other, Rng1, Rng2, C, P1, P2> that)
              : pred_(std::move(that.pred_)), proj1_(std::move(that.proj1_))
              , proj2_(std::move(that.proj2_)), it1_(std::move(that.it1_))
              , end1_(std::move(that.end1_)), it2_(std::move(that.it2_))
              , end2_(std::move(that.end2_))
            {}
            auto CPP_auto_fun(read)() (const)
            (
                return *it1_
            )
            void next()
            {
                ++it1_;
                satisfy();
            }
            CPP_member
            auto equal(set_difference_cursor const &that) const ->
                CPP_ret(bool)(
                    requires ForwardRange<Rng1>)
            {
                // does not support comparing iterators from different ranges
                return it1_ == that.it1_;
            }
            bool equal(default_sentinel_t) const
            {
                return it1_ == end1_;
            }
            auto CPP_auto_fun(move)() (const)
            (
                return iter_move(it1_)
            )
        };

        constexpr cardinality set_difference_cardinality(cardinality c1, cardinality c2)
        {
            return (c1 == unknown) ? unknown :
                (c1 >= 0) || (c1 == finite) ? finite : // else, c1 == infinite
                    (c2 >= 0) || (c2 == finite) ? infinite : unknown;
        }
    }
    /// \endcond

    template<typename Rng1, typename Rng2, typename C, typename P1, typename P2>
    using set_difference_view =
        detail::set_algorithm_view<Rng1, Rng2, C, P1, P2,
            detail::set_difference_cursor,
            detail::set_difference_cardinality(
                range_cardinality<Rng1>::value,
                range_cardinality<Rng2>::value)>;

    namespace view
    {
        struct set_difference_fn
        {
        public:
            template<typename Rng1, typename Rng2, typename C = less,
                typename P1 = identity, typename P2 = identity>
            auto operator()(Rng1 &&rng1, Rng2 &&rng2, C pred = C{}, P1 proj1 = P1{},
                    P2 proj2 = P2{}) const ->
                CPP_ret(set_difference_view<all_t<Rng1>, all_t<Rng2>, C, P1, P2>)(
                    requires ViewableRange<Rng1> && InputRange<Rng1> &&
                        ViewableRange<Rng2> && InputRange<Rng2> &&
                        IndirectRelation<C, projected<iterator_t<Rng1>, P1>,
                                            projected<iterator_t<Rng2>, P2>>)
            {
                return {all(static_cast<Rng1 &&>(rng1)),
                        all(static_cast<Rng2 &&>(rng2)),
                        std::move(pred),
                        std::move(proj1),
                        std::move(proj2)};
            }
        };

        /// \relates set_difference_fn
        /// \ingroup group-views
        RANGES_INLINE_VARIABLE(view<set_difference_fn>, set_difference)
    }
    /// @}

    /// \cond
    namespace detail
    {
        template<bool IsConst,
                 typename Rng1, typename Rng2,
                 typename C, typename P1, typename P2>
        struct set_intersection_cursor
        {
        private:
            friend struct set_intersection_cursor<!IsConst, Rng1, Rng2, C, P1, P2>;
            using pred_ref_ = semiregular_ref_or_val_t<C, IsConst>;
            using proj1_ref_ = semiregular_ref_or_val_t<P1, IsConst>;
            using proj2_ref_ = semiregular_ref_or_val_t<P2, IsConst>;
            pred_ref_ pred_;
            proj1_ref_ proj1_;
            proj2_ref_ proj2_;

            template<typename T>
            using constify_if = meta::const_if_c<IsConst, T>;

            using R1 = constify_if<Rng1>;
            using R2 = constify_if<Rng2>;

            iterator_t<R1> it1_;
            sentinel_t<R1> end1_;

            iterator_t<R2> it2_;
            sentinel_t<R2> end2_;

            void satisfy()
            {
                while(it1_ != end1_ && it2_ != end2_)
                {
                    if(invoke(pred_, invoke(proj1_, *it1_), invoke(proj2_, *it2_)))
                        ++it1_;
                    else
                    {
                        if(!invoke(pred_, invoke(proj2_, *it2_), invoke(proj1_, *it1_)))
                            return;
                        ++it2_;
                    }
                }
            }

        public:
            using value_type = range_value_t<R1>;
            using single_pass = meta::or_c<SinglePass<iterator_t<R1>>,
                                           SinglePass<iterator_t<R2>>>;

            set_intersection_cursor() = default;
            set_intersection_cursor(pred_ref_ pred, proj1_ref_ proj1, proj2_ref_ proj2,
                                    iterator_t<R1> it1, sentinel_t<R1> end1,
                                    iterator_t<R2> it2, sentinel_t<R2> end2)
              : pred_(std::move(pred)), proj1_(std::move(proj1)), proj2_(std::move(proj2)),
                it1_(std::move(it1)), end1_(std::move(end1)), it2_(std::move(it2)), end2_(std::move(end2))
            {
                satisfy();
            }
            CPP_template(bool Other)(
                requires IsConst && (!Other))
            set_intersection_cursor(set_intersection_cursor<Other, Rng1, Rng2, C, P1, P2> that)
              : pred_(std::move(that.pred_)), proj1_(std::move(that.proj1_))
              , proj2_(std::move(that.proj2_)), it1_(std::move(that.it1_))
              , end1_(std::move(that.end1_)), it2_(std::move(that.it2_))
              , end2_(std::move(that.end2_))
            {}
            auto CPP_auto_fun(read)() (const)
            (
                return *it1_
            )
            void next()
            {
                ++it1_;
                ++it2_;
                satisfy();
            }
            CPP_member
            auto equal(set_intersection_cursor const &that) const ->
                CPP_ret(bool)(
                    requires ForwardRange<Rng1>)
            {
                // does not support comparing iterators from different ranges
                return it1_ == that.it1_;
            }
            bool equal(default_sentinel_t) const
            {
                return (it1_ == end1_) || (it2_ == end2_);
            }
            auto CPP_auto_fun(move)() (const)
            (
                return iter_move(it1_)
            )
        };

        constexpr cardinality set_intersection_cardinality(cardinality c1, cardinality c2)
        {
            return (c1 == unknown) || (c2 == unknown) ? unknown :
                   (c1 >= 0 || c1 == finite) || (c2 >= 0 || c2 == finite) ? finite : unknown;
        }
    }
    /// \endcond

    template<typename Rng1, typename Rng2, typename C, typename P1, typename P2>
    using set_intersection_view =
        detail::set_algorithm_view<Rng1, Rng2, C, P1, P2,
            detail::set_intersection_cursor,
            detail::set_intersection_cardinality(
                range_cardinality<Rng1>::value,
                range_cardinality<Rng2>::value)>;

    namespace view
    {
        struct set_intersection_fn
        {
        public:
            template<typename Rng1, typename Rng2, typename C = less,
                typename P1 = identity, typename P2 = identity>
            auto operator()(Rng1 &&rng1, Rng2 &&rng2, C pred = C{}, P1 proj1 = P1{},
                    P2 proj2 = P2{}) const ->
                CPP_ret(set_intersection_view<all_t<Rng1>, all_t<Rng2>, C, P1, P2>)(
                    requires ViewableRange<Rng1> && InputRange<Rng1> &&
                        ViewableRange<Rng2> && InputRange<Rng2> &&
                        IndirectRelation<C, projected<iterator_t<Rng1>, P1>,
                                            projected<iterator_t<Rng2>, P2>>)
            {
                return {all(static_cast<Rng1 &&>(rng1)),
                        all(static_cast<Rng2 &&>(rng2)),
                        std::move(pred),
                        std::move(proj1),
                        std::move(proj2)};
            }
        };

        /// \relates set_intersection_fn
        /// \ingroup group-views
        RANGES_INLINE_VARIABLE(view<set_intersection_fn>, set_intersection)
    }
    /// @}

    /// \cond
    namespace detail
    {
        template<bool IsConst,
                 typename Rng1, typename Rng2,
                 typename C, typename P1, typename P2>
        struct set_union_cursor
        {
        private:
            friend struct set_union_cursor<!IsConst, Rng1, Rng2, C, P1, P2>;
            using pred_ref_ = semiregular_ref_or_val_t<C, IsConst>;
            using proj1_ref_ = semiregular_ref_or_val_t<P1, IsConst>;
            using proj2_ref_ = semiregular_ref_or_val_t<P2, IsConst>;
            pred_ref_ pred_;
            proj1_ref_ proj1_;
            proj2_ref_ proj2_;

            template<typename T>
            using constify_if = meta::const_if_c<IsConst, T>;

            using R1 = constify_if<Rng1>;
            using R2 = constify_if<Rng2>;

            iterator_t<R1> it1_;
            sentinel_t<R1> end1_;

            iterator_t<R2> it2_;
            sentinel_t<R2> end2_;

            enum class state_t
            {
                FIRST, SECOND
            } state;

            void satisfy()
            {
                if(it1_ == end1_)
                {
                    state = state_t::SECOND;
                    return;
                }

                if(it2_ == end2_)
                {
                    state = state_t::FIRST;
                    return;
                }

                if(invoke(pred_, invoke(proj2_, *it2_), invoke(proj1_, *it1_)))
                {
                    state = state_t::SECOND;
                    return;
                }

                if(!invoke(pred_, invoke(proj1_, *it1_), invoke(proj2_, *it2_)))
                    ++it2_;

                state = state_t::FIRST;
            }

        public:
            using value_type = common_type_t<range_value_t<R1>, range_value_t<R2>>;
            using reference_type = common_reference_t<range_reference_t<R1>, range_reference_t<R2>>;
            using rvalue_reference_type = common_reference_t<range_rvalue_reference_t<R1>,
                                                             range_rvalue_reference_t<R2>>;
            using single_pass = meta::or_c<SinglePass<iterator_t<R1>>,
                                           SinglePass<iterator_t<R2>>>;

            set_union_cursor() = default;
            set_union_cursor(pred_ref_ pred, proj1_ref_ proj1, proj2_ref_ proj2,
                             iterator_t<R1> it1, sentinel_t<R1> end1,
                             iterator_t<R2> it2, sentinel_t<R2> end2)
              : pred_(std::move(pred)), proj1_(std::move(proj1)), proj2_(std::move(proj2)),
                it1_(std::move(it1)), end1_(std::move(end1)), it2_(std::move(it2)), end2_(std::move(end2))
            {
                satisfy();
            }
            CPP_template(bool Other)(
                requires IsConst && (!Other))
            set_union_cursor(set_union_cursor<Other, Rng1, Rng2, C, P1, P2> that)
              : pred_(std::move(that.pred_)), proj1_(std::move(that.proj1_))
              , proj2_(std::move(that.proj2_)), it1_(std::move(that.it1_))
              , end1_(std::move(that.end1_)), it2_(std::move(that.it2_))
              , end2_(std::move(that.end2_))
            {}
            reference_type read() const
            noexcept(noexcept(*it1_) && noexcept(*it2_))
            {
                if(state == state_t::SECOND)
                    return *it2_;
                else
                    return *it1_;
            }
            void next()
            {
                if(state == state_t::FIRST)
                    ++it1_;
                else
                    ++it2_;
                satisfy();
            }
            CPP_member
            auto equal(set_union_cursor const &that) const ->
                CPP_ret(bool)(
                    requires ForwardRange<Rng1> && ForwardRange<Rng2>)
            {
                // does not support comparing iterators from different ranges
                return (it1_ == that.it1_) && (it2_ == that.it2_);
            }
            bool equal(default_sentinel_t) const
            {
                return (it1_ == end1_) && (it2_ == end2_);
            }
            rvalue_reference_type move() const
            noexcept(noexcept(iter_move(it1_)) && noexcept(iter_move(it2_)))
            {
                if(state == state_t::SECOND)
                    return iter_move(it2_);
                else
                    return iter_move(it1_);
            }
        };

        constexpr cardinality set_union_cardinality(cardinality c1, cardinality c2)
        {
            return (c1 == infinite) || (c2 == infinite) ? infinite :
                (c1 == unknown) || (c2 == unknown) ? unknown : finite;
        }

    }
    /// \endcond

    template<typename Rng1, typename Rng2, typename C, typename P1, typename P2>
    using set_union_view =
        detail::set_algorithm_view<Rng1, Rng2, C, P1, P2,
            detail::set_union_cursor,
            detail::set_union_cardinality(
                range_cardinality<Rng1>::value,
                range_cardinality<Rng2>::value)>;

    namespace view
    {
        struct set_union_fn
        {
        public:
            template<typename Rng1, typename Rng2, typename C = less,
                typename P1 = identity, typename P2 = identity>
            auto operator()(Rng1 &&rng1, Rng2 &&rng2, C pred = C{}, P1 proj1 = P1{},
                    P2 proj2 = P2{}) const ->
                CPP_ret(set_union_view<all_t<Rng1>, all_t<Rng2>, C, P1, P2>)(
                    requires ViewableRange<Rng1> && InputRange<Rng1> &&
                        ViewableRange<Rng2> && InputRange<Rng2> &&
                        Common<range_value_t<Rng1>, range_value_t<Rng2>> &&
                        CommonReference<range_reference_t<Rng1>, range_reference_t<Rng2>> &&
                        CommonReference<range_rvalue_reference_t<Rng1>,
                                        range_rvalue_reference_t<Rng2>> &&
                        IndirectRelation<C, projected<iterator_t<Rng1>, P1>,
                                            projected<iterator_t<Rng2>, P2>>)
            {
                return {all(static_cast<Rng1 &&>(rng1)),
                        all(static_cast<Rng2 &&>(rng2)),
                        std::move(pred),
                        std::move(proj1),
                        std::move(proj2)};
            }
        };

        /// \relates set_union_fn
        /// \ingroup group-views
        RANGES_INLINE_VARIABLE(view<set_union_fn>, set_union)
    }
    /// @}

    /// \cond
    namespace detail
    {
        template<bool IsConst,
                 typename Rng1, typename Rng2,
                 typename C, typename P1, typename P2>
        struct set_symmetric_difference_cursor
        {
        private:
            friend struct set_symmetric_difference_cursor<!IsConst, Rng1, Rng2, C, P1, P2>;
            using pred_ref_ = semiregular_ref_or_val_t<C, IsConst>;
            using proj1_ref_ = semiregular_ref_or_val_t<P1, IsConst>;
            using proj2_ref_ = semiregular_ref_or_val_t<P2, IsConst>;
            pred_ref_ pred_;
            proj1_ref_ proj1_;
            proj2_ref_ proj2_;

            template<typename T>
            using constify_if = meta::const_if_c<IsConst, T>;

            using R1 = constify_if<Rng1>;
            using R2 = constify_if<Rng2>;

            iterator_t<R1> it1_;
            sentinel_t<R1> end1_;

            iterator_t<R2> it2_;
            sentinel_t<R2> end2_;

            enum class state_t
            {
                FIRST, SECOND, ONLY_FIRST, ONLY_SECOND
            } state;

            void satisfy()
            {
                while(it1_ != end1_)
                {
                    if(it2_ == end2_)
                    {
                        state = state_t::ONLY_FIRST;
                        return;
                    }

                    if(invoke(pred_, invoke(proj1_, *it1_), invoke(proj2_, *it2_)))
                    {
                        state = state_t::FIRST;
                        return;
                    }
                    else
                    {
                        if(invoke(pred_, invoke(proj2_, *it2_), invoke(proj1_, *it1_)))
                        {
                            state = state_t::SECOND;
                            return;
                        }
                        else
                        {
                            ++it1_;
                            ++it2_;
                        }
                    }
                }
                state = state_t::ONLY_SECOND;
            }

        public:
            using value_type = common_type_t<range_value_t<R1>, range_value_t<R2>>;
            using reference_type = common_reference_t<range_reference_t<R1>, range_reference_t<R2>>;
            using rvalue_reference_type = common_reference_t<range_rvalue_reference_t<R1>,
                                                             range_rvalue_reference_t<R2>>;
            using single_pass = meta::or_c<SinglePass<iterator_t<R1>>,
                                           SinglePass<iterator_t<R2>>>;

            set_symmetric_difference_cursor() = default;
            set_symmetric_difference_cursor(pred_ref_ pred, proj1_ref_ proj1, proj2_ref_ proj2,
                                            iterator_t<R1> it1, sentinel_t<R1> end1,
                                            iterator_t<R2> it2, sentinel_t<R2> end2)
              : pred_(std::move(pred)), proj1_(std::move(proj1)), proj2_(std::move(proj2)),
                it1_(std::move(it1)), end1_(std::move(end1)), it2_(std::move(it2)), end2_(std::move(end2)),
                state()
            {
                satisfy();
            }
            CPP_template(bool Other)(
                requires IsConst && (!Other))
            set_symmetric_difference_cursor(
                set_symmetric_difference_cursor<Other, Rng1, Rng2, C, P1, P2> that)
              : pred_(std::move(that.pred_)), proj1_(std::move(that.proj1_))
              , proj2_(std::move(that.proj2_)), it1_(std::move(that.it1_))
              , end1_(std::move(that.end1_)), it2_(std::move(that.it2_))
              , end2_(std::move(that.end2_)), state(that.state)
            {}
            reference_type read() const
            noexcept(noexcept(*it1_) && noexcept(*it2_))
            {
                if(state == state_t::SECOND || state == state_t::ONLY_SECOND)
                    return *it2_;
                else
                    return *it1_;
            }
            void next()
            {
                switch(state)
                {
                    case state_t::FIRST:
                        ++it1_;
                        satisfy();
                        break;
                    case state_t::ONLY_FIRST:
                        ++it1_;
                        break;
                    case state_t::SECOND:
                        ++it2_;
                        satisfy();
                        break;
                    case state_t::ONLY_SECOND:
                        ++it2_;
                        break;
                }
            }
            CPP_member
            auto equal(set_symmetric_difference_cursor const &that) const ->
                CPP_ret(bool)(
                    requires ForwardRange<R1> && ForwardRange<R2>)
            {
                // does not support comparing iterators from different ranges:
                return (it1_ == that.it1_) && (it2_ == that.it2_);
            }
            bool equal(default_sentinel_t) const
            {
                return (it1_ == end1_) && (it2_ == end2_);
            }
            rvalue_reference_type move() const
            noexcept(noexcept(iter_move(it1_)) && noexcept(iter_move(it2_)))
            {
                if(state == state_t::SECOND || state == state_t::ONLY_SECOND)
                    return iter_move(it2_);
                else
                    return iter_move(it1_);
            }
        };

        constexpr cardinality set_symmetric_difference_cardinality(cardinality c1, cardinality c2)
        {
            return (c1 == unknown) || (c2 == unknown) ? unknown :
                (c1 == infinite) != (c2 == infinite) ? infinite :
                    (c1 == infinite) && (c2 == infinite) ? unknown : finite;
        }

    }
    /// \endcond

    template<typename Rng1, typename Rng2, typename C, typename P1, typename P2>
    using set_symmetric_difference_view =
        detail::set_algorithm_view<Rng1, Rng2, C, P1, P2,
            detail::set_symmetric_difference_cursor,
            detail::set_symmetric_difference_cardinality(
                range_cardinality<Rng1>::value,
                range_cardinality<Rng2>::value)>;

    namespace view
    {
        struct set_symmetric_difference_fn
        {
        public:
            template<typename Rng1, typename Rng2, typename C = less,
                typename P1 = identity, typename P2 = identity>
            auto operator()(Rng1 &&rng1, Rng2 &&rng2, C pred = C{}, P1 proj1 = P1{},
                    P2 proj2 = P2{}) const ->
                CPP_ret(set_symmetric_difference_view<all_t<Rng1>, all_t<Rng2>, C, P1, P2>)(
                    requires ViewableRange<Rng1> && InputRange<Rng1> &&
                        ViewableRange<Rng2> && InputRange<Rng2> &&
                        Common<range_value_t<Rng1>, range_value_t<Rng2>> &&
                        CommonReference<range_reference_t<Rng1>, range_reference_t<Rng2>> &&
                        CommonReference<range_rvalue_reference_t<Rng1>,
                                        range_rvalue_reference_t<Rng2>> &&
                        IndirectRelation<C, projected<iterator_t<Rng1>, P1>,
                                            projected<iterator_t<Rng2>, P2>>)
            {
                return {all(static_cast<Rng1 &&>(rng1)),
                        all(static_cast<Rng2 &&>(rng2)),
                        std::move(pred),
                        std::move(proj1),
                        std::move(proj2)};
            }
        };

        /// \relates set_symmetric_difference_fn
        /// \ingroup group-views
        RANGES_INLINE_VARIABLE(view<set_symmetric_difference_fn>, set_symmetric_difference)
    }
    /// @}
}

#endif
