名前空間
変種
操作

標準ライブラリヘッダ <ranges>

提供: cppreference.com
< cpp‎ | header
 
 
 

このヘッダは範囲ライブラリの一部です。

目次

[編集] 名前空間エイリアス

namespace std {

    namespace view = ranges::view;

}

std::ranges::view の短縮形として名前空間エイリアス std::view が提供されます。

コンセプト

範囲コンセプト
名前空間 std::ranges で定義
型が範囲である、つまり、 begin イテレータと end 番兵を提供することを指定します
(コンセプト) [edit]
範囲のサイズを定数時間で取得できることを指定します
(コンセプト) [edit]
範囲がビューである、つまり、コピー/ムーブ/代入が定数時間であることを指定します
(コンセプト) [edit]
イテレータの型が InputIterator を満たす範囲を指定します
(コンセプト) [edit]
イテレータの型が OutputIterator を満たす範囲を指定します
(コンセプト) [edit]
イテレータの型が ForwardIterator を満たす範囲を指定します
(コンセプト) [edit]
イテレータの型が BidirectionalIterator を満たす範囲を指定します
(コンセプト) [edit]
イテレータの型が RandomAccessIterator を満たす範囲を指定します
(コンセプト) [edit]
イテレータの型が ContiguousIterator を満たす範囲を指定します
(コンセプト) [edit]
範囲のイテレータと番兵の型が同一であることを指定します
(コンセプト) [edit]
View に安全に変換可能であるための Range に対する要件を指定します
(コンセプト) [edit]

クラス

範囲プリミティブ
名前空間 std::ranges で定義
範囲のイテレータおよび番兵の型を取得します
(エイリアステンプレート) [edit]
ビュー
名前空間 std::ranges で定義
奇妙に再帰したテンプレートパターンを用いた View を定義するためのヘルパークラステンプレート
(クラステンプレート) [edit]
イテレータと番兵の組を結合して View にします
(クラステンプレート) [edit]
ダングリングイテレータ対策
名前空間 std::ranges で定義
ダングリングになるであろうためにイテレータまたは subrange が返されるべきではないことを表すプレースホルダ型
(クラス) [edit]
__ForwardingRange もモデル化する Range のイテレータ型または subrange 型を取得します
(エイリアステンプレート) [edit]
ファクトリ
名前空間 std::ranges で定義
要素を持たない空の View
(クラステンプレート) (変数テンプレート) [edit]
指定された値の要素1個を格納する View
(クラステンプレート) (カスタマイゼーションポイントオブジェクト) [edit]
初期値を繰り返しインクリメントすることによって生成されるシーケンスから構成される View
(クラステンプレート) (カスタマイゼーションポイントオブジェクト) [edit]
イテレータとカウントから部分範囲を作成します
(カスタマイゼーションポイントオブジェクト) [edit]
アダプタ
名前空間 std::ranges で定義
Range のすべての要素を含む View
(エイリアステンプレート) (範囲アダプタオブジェクト) [edit]
何らかの他の Range の要素の View
(クラステンプレート) [edit]
述語を満たす Range の要素から構成される View
(クラステンプレート) (範囲アダプタオブジェクト) [edit]
各要素に変換関数を適用するシーケンスの View
(クラステンプレート) (範囲アダプタオブジェクト) [edit]
別の View の最初の N 個の要素から構成される View
(クラステンプレート) (範囲アダプタオブジェクト) [edit]
RangeView を平坦化することによって得られるシーケンスから構成される View
(クラステンプレート) (範囲アダプタオブジェクト) [edit]
別の View を区切り文字で分割することによって得られる部分範囲群に対する View
(クラステンプレート) (範囲アダプタオブジェクト) [edit]
ViewCommonRange に変換します
(クラステンプレート) (範囲アダプタオブジェクト) [edit]
別の双方向ビューの要素を逆順でイテレートする View
(クラステンプレート) (範囲アダプタオブジェクト) [edit]

カスタマイゼーションポイントオブジェクト

範囲アクセス
名前空間 std::ranges で定義
範囲の先頭を指すイテレータを返します
(カスタマイゼーションポイントオブジェクト) [edit]
(C++20)
範囲の終端を指すイテレータを返します
(カスタマイゼーションポイントオブジェクト) [edit]
範囲の逆イテレータを返します
(カスタマイゼーションポイントオブジェクト) [edit]
(C++20)
範囲の逆終端イテレータを返します
(カスタマイゼーションポイントオブジェクト) [edit]
(C++20)
サイズが定数時間で計算可能な範囲のサイズを取得します
(カスタマイゼーションポイントオブジェクト) [edit]
(C++20)
範囲が空かどうか調べます
(カスタマイゼーションポイントオブジェクト) [edit]
(C++20)
隣接範囲の先頭を指すポインタを取得します
(カスタマイゼーションポイントオブジェクト) [edit]

[編集] 概要

#include <initializer_list>
#include <iterator>
 
namespace std::ranges {
  inline namespace /* unspecified */ {
    // range access
    inline constexpr /* unspecified */ begin = /* unspecified */;
    inline constexpr /* unspecified */ end = /* unspecified */;
    inline constexpr /* unspecified */ cbegin = /* unspecified */;
    inline constexpr /* unspecified */ cend = /* unspecified */;
    inline constexpr /* unspecified */ rbegin = /* unspecified */;
    inline constexpr /* unspecified */ rend = /* unspecified */;
    inline constexpr /* unspecified */ crbegin = /* unspecified */;
    inline constexpr /* unspecified */ crend = /* unspecified */;
 
    inline constexpr /* unspecified */ size = /* unspecified */;
    inline constexpr /* unspecified */ empty = /* unspecified */;
    inline constexpr /* unspecified */ data = /* unspecified */;
    inline constexpr /* unspecified */ cdata = /* unspecified */;
  }
 
  // ranges
  template<class T>
    using iterator_t = decltype(ranges::begin(declval<T&>()));
 
  template<class T>
    using sentinel_t = decltype(ranges::end(declval<T&>()));
 
  template<class T>
    concept Range = /* see definition */;
 
  // sized ranges
  template<class>
    inline constexpr bool disable_sized_range = false;
 
  template<class T>
    concept SizedRange = /* see definition */;
 
  // views
  template<class T>
    inline constexpr bool enable_view = /* see definition */;
 
  struct view_base { };
 
  template<class T>
    concept View = /* see definition */;
 
  // other range refinements
  template<class R, class T>
    concept OutputRange = /* see definition */;
 
  template<class T>
    concept InputRange = /* see definition */;
 
  template<class T>
    concept ForwardRange = /* see definition */;
 
  template<class T>
    concept BidirectionalRange = /* see definition */;
 
  template<class T>
    concept RandomAccessRange = /* see definition */;
 
  template<class T>
    concept ContiguousRange = /* see definition */;
 
  template<class T>
    concept CommonRange = /* see definition */;
 
  template<class T>
    concept ViewableRange = /* see definition */;
 
  // class template view_interface
  template<class D>
    requires is_class_v<D> && Same<D, remove_cv_t<D>>
  class view_interface;
 
  // sub-ranges
  enum class subrange_kind : bool { unsized, sized };
 
  template<Iterator I, Sentinel<I> S = I, subrange_kind K = /* see definition */>
    requires (K == subrange_kind::sized || !SizedSentinel<S, I>)
  class subrange;
 
  // dangling iterator handling
  struct dangling;
 
  template<Range R>
    using safe_iterator_t = conditional_t<__ForwardingRange<R>, iterator_t<R>, dangling>;
 
  template<Range R>
    using safe_subrange_t =
      conditional_t<__ForwardingRange<R>, subrange<iterator_t<R>>, dangling>;
 
  // empty view
  template<class T>
    requires is_object_v<T>
  class empty_view;
 
  namespace view {
    template<class T>
      inline constexpr empty_view<T> empty{};
  }
 
  // single view
  template<CopyConstructible T>
    requires is_object_v<T>
  class single_view;
 
  namespace view { inline constexpr /* unspecified */ single = /* unspecified */; }
 
  // iota view
  template<WeaklyIncrementable W, Semiregular Bound = unreachable_sentinel_t>
    requires __WeaklyEqualityComparableWith<W, Bound>
  class iota_view;
 
  namespace view { inline constexpr /* unspecified */ iota = /* unspecified */; }
 
  // all view
  namespace view { inline constexpr /* unspecified */ all = /* unspecified */; }
 
  template<ViewableRange R>
    using all_view = decltype(view::all(declval<R>()));
 
  template<Range R>
    requires is_object_v<R>
  class ref_view;
 
  // filter view
  template<InputRange V, IndirectUnaryPredicate<iterator_t<V>> Pred>
    requires View<V> && is_object_v<Pred>
  class filter_view;
 
  namespace view { inline constexpr /* unspecified */ filter = /* unspecified */; }
 
  // transform view
  template<InputRange V, CopyConstructible F>
    requires View<V> && is_object_v<F> &&
             RegularInvocable<F&, iter_reference_t<iterator_t<V>>>
  class transform_view;
 
  namespace view { inline constexpr /* unspecified */ transform = /* unspecified */; }
 
  // take view
  template<View> class take_view;
 
  namespace view { inline constexpr /* unspecified */ take = /* unspecified */; }
 
  // join view
  template<InputRange V>
    requires View<V> && InputRange<iter_reference_t<iterator_t<V>>> &&
             (is_reference_v<iter_reference_t<iterator_t<V>>> ||
              View<iter_value_t<iterator_t<V>>>)
  class join_view;
 
  namespace view { inline constexpr /* unspecified */ join = /* unspecified */; }
 
  // split view
  template<class R>
    concept __TinyRange = /* see definition */;   // exposition only
 
  template<InputRange V, ForwardRange Pattern>
    requires View<V> && View<Pattern> &&
             IndirectlyComparable<iterator_t<V>, iterator_t<Pattern>, ranges::equal_to> &&
             (ForwardRange<V> || __TinyRange<Pattern>)
  class split_view;
 
  namespace view { inline constexpr /* unspecified */ split = /* unspecified */; }
 
  // counted view
  namespace view { inline constexpr /* unspecified */ counted = /* unspecified */; }
 
  // common view
  template<View V>
    requires (!CommonRange<V>)
  class common_view;
 
  namespace view { inline constexpr /* unspecified */ common = /* unspecified */; }
 
  // reverse view
  template<View V>
    requires BidirectionalRange<V>
  class reverse_view;
 
  namespace view { inline constexpr /* unspecified */ reverse = /* unspecified */; }
}
 
namespace std {
  namespace view = ranges::view;
 
  template<class I, class S, ranges::subrange_kind K>
  struct tuple_size<ranges::subrange<I, S, K>>
    : integral_constant<size_t, 2> {};
  template<class I, class S, ranges::subrange_kind K>
  struct tuple_element<0, ranges::subrange<I, S, K>> {
    using type = I;
  };
  template<class I, class S, ranges::subrange_kind K>
  struct tuple_element<1, ranges::subrange<I, S, K>> {
    using type = S;
  };
}

[編集] コンセプト Range

namespace std::ranges {
  template<class T>
    concept __RangeImpl =          // exposition only
      requires(T&& t) {
        ranges::begin(std::forward<T>(t));// sometimes equality-preserving (see definition)
        ranges::end(std::forward<T>(t));
      };
 
  template<class T>
    concept Range = __RangeImpl<T&>;
 
  template<class T>
    concept __ForwardingRange =    // exposition only
      Range<T> && __RangeImpl<T>;
}

[編集] コンセプト SizedRange

namespace std::ranges {
  template<class T>
    concept SizedRange =
      Range<T> &&
      !disable_sized_range<remove_cvref_t<T>> &&
      requires(T& t) { ranges::size(t); };
}

[編集] コンセプト View

namespace std::ranges {
  template<class T>
    inline constexpr bool enable_view = /* see definition */;
 
  template<class T>
    concept View =
      Range<T> && Semiregular<T> && enable_view<T>;
}


[編集] コンセプト OutputRange

namespace std::ranges {
  template<class R, class T>
    concept OutputRange =
      Range<R> && OutputIterator<iterator_t<R>, T>;
}

[編集] コンセプト InputRange

namespace std::ranges {
  template<class T>
    concept InputRange =
      Range<T> && InputIterator<iterator_t<T>>;
}

[編集] コンセプト ForwardRange

namespace std::ranges {
  template<class T>
    concept ForwardRange =
      InputRange<T> && ForwardIterator<iterator_t<T>>;
}

[編集] コンセプト BidirectionalRange

namespace std::ranges {
  template<class T>
    concept BidirectionalRange =
      ForwardRange<T> && BidirectionalIterator<iterator_t<T>>;
}

[編集] コンセプト RandomAccessRange

namespace std::ranges {
  template<class T>
    concept RandomAccessRange =
      BidirectionalRange<T> && RandomAccessIterator<iterator_t<T>>;
}

[編集] コンセプト ContiguousRange

namespace std::ranges {
  template<class T>
    concept ContiguousRange =
     RandomAccessRange<T> && ContiguousIterator<iterator_t<T>> &&
      requires(T& t) {
        { ranges::data(t) } -> Same<add_pointer_t<iter_reference_t<iterator_t<T>>>>;
      };
}

[編集] コンセプト CommonRange

namespace std::ranges {
  template<class T>
    concept CommonRange =
      Range<T> && Same<iterator_t<T>, sentinel_t<T>>;
}

[編集] コンセプト ViewableRange

namespace std::ranges {
  template<class T>
    concept ViewableRange =
      Range<T> && (__ForwardingRange<T> || View<decay_t<T>>);
}

[編集] ヘルパーコンセプト

namespace std::ranges { // unspecified, for name lookup only
  template<class R>
    concept __SimpleView =                        // exposition only
      View<R> && Range<const R> &&
      Same<iterator_t<R>, iterator_t<const R>> &&
      Same<sentinel_t<R>, sentinel_t<const R>>;
 
  template<InputIterator I>
    concept __HasArrow =                          // exposition only
      is_pointer_v<I> || requires(I i) { i.operator->(); };
 
  template<class T, class U>
    concept __NotSameAs =                         // exposition only
      !Same<remove_cvref_t<T>, remove_cvref_t<U>>;
 
  template<class I>
    concept _Decrementable =                      // exposition only
      Incrementable<I> && requires(I i) {
        { --i } -> Same<I&>;
        { i-- } -> Same<I>;
      };
 
  template<class I>
    concept _Advanceable =                        // exposition only
      _Decrementable<I> && StrictTotallyOrdered<I> &&
      requires(I i, const I j, const iter_difference_t<I> n) {
        { i += n } -> Same<I&>;
        { i -= n } -> Same<I&>;
        { j +  n } -> Same<I>;
        { n +  j } -> Same<I>;
        { j -  n } -> Same<I>;
        { j -  j } -> Same<iter_difference_t<I>>;
      };
}

注: これらの名前は説明専用であり、インタフェースの一部ではありません。

[編集] クラステンプレート std::ranges::view_interface

namespace std::ranges {
  template<class D>
    requires is_class_v<D> && Same<D, remove_cv_t<D>>
  class view_interface : public view_base {
  private:
    constexpr D& derived() noexcept {                   // exposition only
      return static_cast<D&>(*this);
    }
    constexpr const D& derived() const noexcept {       // exposition only
      return static_cast<const D&>(*this);
    }
  public:
    constexpr bool empty() requires ForwardRange<D> {
      return ranges::begin(derived()) == ranges::end(derived());
    }
    constexpr bool empty() const requires ForwardRange<const D> {
      return ranges::begin(derived()) == ranges::end(derived());
    }
 
    constexpr explicit operator bool()
      requires requires { ranges::empty(derived()); } {
        return !ranges::empty(derived());
      }
    constexpr explicit operator bool() const
      requires requires { ranges::empty(derived()); } {
        return !ranges::empty(derived());
      }
 
    constexpr auto data() requires ContiguousIterator<iterator_t<D>> {
      return ranges::empty(derived()) ? nullptr : addressof(*ranges::begin(derived()));
    }
    constexpr auto data() const
      requires Range<const D> && ContiguousIterator<iterator_t<const D>> {
        return ranges::empty(derived()) ? nullptr : addressof(*ranges::begin(derived()));
      }
 
    constexpr auto size() requires ForwardRange<D> &&
      SizedSentinel<sentinel_t<D>, iterator_t<D>> {
        return ranges::end(derived()) - ranges::begin(derived());
      }
    constexpr auto size() const requires ForwardRange<const D> &&
      SizedSentinel<sentinel_t<const D>, iterator_t<const D>> {
        return ranges::end(derived()) - ranges::begin(derived());
      }
 
    constexpr decltype(auto) front() requires ForwardRange<D>;
    constexpr decltype(auto) front() const requires ForwardRange<const D>;
 
    constexpr decltype(auto) back() requires BidirectionalRange<D> && CommonRange<D>;
    constexpr decltype(auto) back() const
      requires BidirectionalRange<const D> && CommonRange<const D>;
 
    template<RandomAccessRange R = D>
      constexpr decltype(auto) operator[](iter_difference_t<iterator_t<R>> n) {
        return ranges::begin(derived())[n];
      }
    template<RandomAccessRange R = const D>
      constexpr decltype(auto) operator[](iter_difference_t<iterator_t<R>> n) const {
        return ranges::begin(derived())[n];
      }
  };
}

[編集] クラステンプレート std::ranges::subrange

namespace std::ranges {
  template<class T>
    concept __PairLike =                                // exposition only
      !is_reference_v<T> && requires(T t) {
        typename tuple_size<T>::type;   // ensures tuple_­size<T> is complete
        requires DerivedFrom<tuple_size<T>, integral_constant<size_t, 2>>;
        typename tuple_element_t<0, remove_const_t<T>>;
        typename tuple_element_t<1, remove_const_t<T>>;
        { get<0>(t) } -> const tuple_element_t<0, T>&;
        { get<1>(t) } -> const tuple_element_t<1, T>&;
      };
 
  template<class T, class U, class V>
    concept __PairLikeConvertibleTo =                   // exposition only
      !Range<T> && __PairLike<remove_reference_t<T>> &&
      requires(T&& t) {
        { get<0>(std::forward<T>(t)) } -> ConvertibleTo<U>;
        { get<1>(std::forward<T>(t)) } -> ConvertibleTo<V>;
      };
 
  template<class T, class U, class V>
    concept __PairLikeConvertibleFrom =                 // exposition only
      !Range<T> && __PairLike<T> && Constructible<T, U, V>;
 
  template<class T>
    concept __IteratorSentinelPair =                    // exposition only
      !Range<T> && __PairLike<T> &&
      Sentinel<tuple_element_t<1, T>, tuple_element_t<0, T>>;
 
  template<Iterator I, Sentinel<I> S = I, subrange_kind K =
      SizedSentinel<S, I> ? subrange_kind::sized : subrange_kind::unsized>
    requires (K == subrange_kind::sized || !SizedSentinel<S, I>)
  class subrange : public view_interface<subrange<I, S, K>> {
  private:
    static constexpr bool StoreSize =                   // exposition only
      K == subrange_kind::sized && !SizedSentinel<S, I>;
    I begin_ = I();                                     // exposition only
    S end_ = S();                                       // exposition only
    iter_difference_t<I> size_ = 0;                     // exposition only; present only
                                                        // when StoreSize is true
  public:
    subrange() = default;
 
    constexpr subrange(I i, S s) requires (!StoreSize);
 
    constexpr subrange(I i, S s, iter_difference_t<I> n)
      requires (K == subrange_kind::sized);
 
    template<__NotSameAs<subrange> R>
      requires __ForwardingRange<R> &&
        ConvertibleTo<iterator_t<R>, I> && ConvertibleTo<sentinel_t<R>, S>
    constexpr subrange(R&& r) requires (!StoreSize || SizedRange<R>);
 
    template<__ForwardingRange R>
      requires ConvertibleTo<iterator_t<R>, I> && ConvertibleTo<sentinel_t<R>, S>
    constexpr subrange(R&& r, iter_difference_t<I> n)
      requires (K == subrange_kind::sized)
        : subrange{ranges::begin(r), ranges::end(r), n}
    {}
 
    template<__NotSameAs<subrange> PairLike>
      requires __PairLikeConvertibleTo<PairLike, I, S>
    constexpr subrange(PairLike&& r) requires (!StoreSize)
      : subrange{std::get<0>(std::forward<PairLike>(r)),
                 std::get<1>(std::forward<PairLike>(r))}
    {}
 
    template<__PairLikeConvertibleTo<I, S> PairLike>
    constexpr subrange(PairLike&& r, iter_difference_t<I> n)
      requires (K == subrange_kind::sized)
      : subrange{std::get<0>(std::forward<PairLike>(r)),
                 std::get<1>(std::forward<PairLike>(r)), n}
    {}
 
    template<__NotSameAs<subrange> PairLike>
      requires __PairLikeConvertibleFrom<PairLike, const I&, const S&>
    constexpr operator PairLike() const;
 
    constexpr I begin() const;
    constexpr S end() const;
 
    constexpr bool empty() const;
    constexpr iter_difference_t<I> size() const
      requires (K == subrange_kind::sized);
 
    [[nodiscard]] constexpr subrange next(iter_difference_t<I> n = 1) const;
    [[nodiscard]] constexpr subrange prev(iter_difference_t<I> n = 1) const
      requires BidirectionalIterator<I>;
    constexpr subrange& advance(iter_difference_t<I> n);
 
    friend constexpr I begin(subrange&& r) { return r.begin(); }
    friend constexpr S end(subrange&& r) { return r.end(); }
  };
 
  template<Iterator I, Sentinel<I> S>
    subrange(I, S, iter_difference_t<I>) -> subrange<I, S, subrange_kind::sized>;
 
  template<__IteratorSentinelPair P>
    subrange(P) -> subrange<tuple_element_t<0, P>, tuple_element_t<1, P>>;
 
  template<__IteratorSentinelPair P>
    subrange(P, iter_difference_t<tuple_element_t<0, P>>) ->
      subrange<tuple_element_t<0, P>, tuple_element_t<1, P>, subrange_kind::sized>;
 
  template<__ForwardingRange R>
    subrange(R&&) ->
      subrange<iterator_t<R>, sentinel_t<R>,
               (SizedRange<R> || SizedSentinel<sentinel_t<R>, iterator_t<R>>)
                 ? subrange_kind::sized : subrange_kind::unsized>;
 
  template<__ForwardingRange R>
    subrange(R&&, iter_difference_t<iterator_t<R>>) ->
      subrange<iterator_t<R>, sentinel_t<R>, subrange_kind::sized>;
 
  template<size_t N, class I, class S, subrange_kind K>
    requires (N < 2)
  constexpr auto get(const subrange<I, S, K>& r);
}
 
namespace std {
  using ranges::get;
}

[編集] クラス std::ranges::dangling

namespace std::ranges {
  struct dangling {
    constexpr dangling() noexcept = default;
    template<class... Args>
      constexpr dangling(Args&&...) noexcept { }
  };
}

[編集] クラステンプレート std::ranges::empty_view

namespace std::ranges {
  template<class T>
    requires is_object_v<T>
  class empty_view : public view_interface<empty_view<T>> {
  public:
    static constexpr T* begin() noexcept { return nullptr; }
    static constexpr T* end() noexcept { return nullptr; }
    static constexpr T* data() noexcept { return nullptr; }
    static constexpr ptrdiff_t size() noexcept { return 0; }
    static constexpr bool empty() noexcept { return true; }
 
    friend constexpr T* begin(empty_view) noexcept { return nullptr; }
    friend constexpr T* end(empty_view) noexcept { return nullptr; }
  };
}

[編集] クラステンプレート std::ranges:: single_view

namespace std::ranges {
  template<CopyConstructible T>
    requires is_object_v<T>
  class single_view : public view_interface<single_view<T>> {
  private:
    semiregular_box<T> value_;  // exposition only
  public:
    single_view() = default;
    constexpr explicit single_view(const T& t);
    constexpr explicit single_view(T&& t);
    template<class... Args>
      requires Constructible<T, Args...>
    constexpr single_view(in_place_t, Args&&... args);
 
    constexpr T* begin() noexcept;
    constexpr const T* begin() const noexcept;
    constexpr T* end() noexcept;
    constexpr const T* end() const noexcept;
    static constexpr ptrdiff_t size() noexcept;
    constexpr T* data() noexcept;
    constexpr const T* data() const noexcept;
  };
}

[編集] クラステンプレート std::ranges::iota_view

namespace std::ranges {
  template<class I>
    concept _Decrementable =    // exposition only
      /* see definition */;
  template<class I>
    concept _Advanceable =      // exposition only
      /* see definition */;
 
  template<WeaklyIncrementable W, Semiregular Bound = unreachable_sentinel_t>
    requires __WeaklyEqualityComparableWith<W, Bound>
  class iota_view : public view_interface<iota_view<W, Bound>> {
  private:
    // class iota_­view​::​iterator
    struct iterator;            // exposition only
    // class iota_­view​::​sentinel
    struct sentinel;            // exposition only
    W value_ = W();             // exposition only
    Bound bound_ = Bound();     // exposition only
  public:
    iota_view() = default;
    constexpr explicit iota_view(W value);
    constexpr iota_view(type_identity_t<W> value,
                        type_identity_t<Bound> bound);
 
    constexpr iterator begin() const;
    constexpr sentinel end() const;
    constexpr iterator end() const requires Same<W, Bound>;
 
    constexpr auto size() const
      requires (Same<W, Bound> && _Advanceable<W>) ||
               (Integral<W> && Integral<Bound>) ||
               SizedSentinel<Bound, W>
    { return bound_ - value_; }
  };
 
  template<class W, class Bound>
    requires (!Integral<W> || !Integral<Bound> || is_signed_v<W> == is_signed_v<Bound>)
  iota_view(W, Bound) -> iota_view<W, Bound>;
}

[編集] クラス std::ranges::iota_view::iterator

namespace std::ranges {
  template<class W, class Bound>
  struct iota_view<W, Bound>::iterator {
  private:
    W value_ = W();             // exposition only
  public:
    using iterator_category = /* see definition */;
    using value_type = W;
    using difference_type = iter_difference_t<W>;
 
    iterator() = default;
    constexpr explicit iterator(W value);
 
    constexpr W operator*() const noexcept(is_nothrow_copy_constructible_v<W>);
 
    constexpr iterator& operator++();
    constexpr void operator++(int);
    constexpr iterator operator++(int) requires Incrementable<W>;
 
    constexpr iterator& operator--() requires _Decrementable<W>;
    constexpr iterator operator--(int) requires _Decrementable<W>;
 
    constexpr iterator& operator+=(difference_type n)
      requires _Advanceable<W>;
    constexpr iterator& operator-=(difference_type n)
      requires _Advanceable<W>;
    constexpr W operator[](difference_type n) const
      requires _Advanceable<W>;
 
    friend constexpr bool operator==(const iterator& x, const iterator& y)
      requires EqualityComparable<W>;
    friend constexpr bool operator!=(const iterator& x, const iterator& y)
      requires EqualityComparable<W>;
 
    friend constexpr bool operator<(const iterator& x, const iterator& y)
      requires StrictTotallyOrdered<W>;
    friend constexpr bool operator>(const iterator& x, const iterator& y)
      requires StrictTotallyOrdered<W>;
    friend constexpr bool operator<=(const iterator& x, const iterator& y)
      requires StrictTotallyOrdered<W>;
    friend constexpr bool operator>=(const iterator& x, const iterator& y)
      requires StrictTotallyOrdered<W>;
 
    friend constexpr iterator operator+(iterator i, difference_type n)
      requires _Advanceable<W>;
    friend constexpr iterator operator+(difference_type n, iterator i)
      requires _Advanceable<W>;
 
    friend constexpr iterator operator-(iterator i, difference_type n)
      requires _Advanceable<W>;
    friend constexpr difference_type operator-(const iterator& x, const iterator& y)
      requires _Advanceable<W>;
  };
}

[編集] クラス std::ranges::iota_view::sentinel

namespace std::ranges {
  template<class W, class Bound>
  struct iota_view<W, Bound>::sentinel {
  private:
    Bound bound_ = Bound();     // exposition only
  public:
    sentinel() = default;
    constexpr explicit sentinel(Bound bound);
 
    friend constexpr bool operator==(const iterator& x, const sentinel& y);
    friend constexpr bool operator==(const sentinel& x, const iterator& y);
    friend constexpr bool operator!=(const iterator& x, const sentinel& y);
    friend constexpr bool operator!=(const sentinel& x, const iterator& y);
  };
}

[編集] クラステンプレート std::ranges::ref_view

namespace std::ranges {
  template<Range R>
    requires is_object_v<R>
  class ref_view : public view_interface<ref_view<R>> {
  private:
    R* r_ = nullptr;            // exposition only
  public:
    constexpr ref_view() noexcept = default;
 
    template<__NotSameAs<ref_view> T>
      requires /* see definition */
    constexpr ref_view(T&& t);
 
    constexpr R& base() const { return *r_; }
 
    constexpr iterator_t<R> begin() const { return ranges::begin(*r_); }
    constexpr sentinel_t<R> end() const { return ranges::end(*r_); }
 
    constexpr bool empty() const
      requires requires { ranges::empty(*r_); }
    { return ranges::empty(*r_); }
 
    constexpr auto size() const requires SizedRange<R>
    { return ranges::size(*r_); }
 
    constexpr auto data() const requires ContiguousRange<R>
    { return ranges::data(*r_); }
 
    friend constexpr iterator_t<R> begin(ref_view r)
    { return r.begin(); }
 
    friend constexpr sentinel_t<R> end(ref_view r)
    { return r.end(); }
  };
  template<class R>
    ref_view(R&) -> ref_view<R>;
}

[編集] クラステンプレート std::ranges::filter_view

namespace std::ranges {
  template<InputRange V, IndirectUnaryPredicate<iterator_t<V>> Pred>
    requires View<V> && is_object_v<Pred>
  class filter_view : public view_interface<filter_view<V, Pred>> {
  private:
    V base_ = V();                  // exposition only
    semiregular_box<Pred> pred_;    // exposition only
 
    // class filter_view​::​iterator
    class iterator;                 // exposition only
    // class filter_view​::​sentinel
    class sentinel;                 // exposition only
 
  public:
    filter_view() = default;
    constexpr filter_view(V base, Pred pred);
    template<InputRange R>
      requires ViewableRange<R> && Constructible<V, all_view<R>>
    constexpr filter_view(R&& r, Pred pred);
 
    constexpr V base() const;
 
    constexpr iterator begin();
    constexpr auto end() {
      if constexpr (CommonRange<V>)
        return iterator{*this, ranges::end(base_)};
      else
        return sentinel{*this};
    }
  };
 
  template<class R, class Pred>
    filter_view(R&&, Pred) -> filter_view<all_view<R>, Pred>;
}

[編集] クラス std::ranges::filter_view::iterator

namespace std::ranges {
  template<class V, class Pred>
  class filter_view<V, Pred>::iterator {
  private:
    iterator_t<V> current_ = iterator_t<V>();   // exposition only
    filter_view* parent_ = nullptr;             // exposition only
  public:
    using iterator_concept  = /* see definition */;
    using iterator_category = /* see definition */;
    using value_type        = iter_value_t<iterator_t<V>>;
    using difference_type   = iter_difference_t<iterator_t<V>>;
 
    iterator() = default;
    constexpr iterator(filter_view& parent, iterator_t<V> current);
 
    constexpr iterator_t<V> base() const;
    constexpr iter_reference_t<iterator_t<V>> operator*() const;
    constexpr iterator_t<V> operator->() const
      requires has-arrow<iterator_t<V>>;
 
    constexpr iterator& operator++();
    constexpr void operator++(int);
    constexpr iterator operator++(int) requires ForwardRange<V>;
 
    constexpr iterator& operator--() requires BidirectionalRange<V>;
    constexpr iterator operator--(int) requires BidirectionalRange<V>;
 
    friend constexpr bool operator==(const iterator& x, const iterator& y)
      requires EqualityComparable<iterator_t<V>>;
    friend constexpr bool operator!=(const iterator& x, const iterator& y)
      requires EqualityComparable<iterator_t<V>>;
 
    friend constexpr iter_rvalue_reference_t<iterator_t<V>> iter_move(const iterator& i)
      noexcept(noexcept(ranges::iter_move(i.current_)));
    friend constexpr void iter_swap(const iterator& x, const iterator& y)
      noexcept(noexcept(ranges::iter_swap(x.current_, y.current_)))
      requires IndirectlySwappable<iterator_t<V>>;
  };
}

[編集] クラス std::ranges::filter_view::sentinel

namespace std::ranges {
  template<class V, class Pred>
  class filter_view<V, Pred>::sentinel {
  private:
    sentinel_t<V> end_ = sentinel_t<V>();       // exposition only
  public:
    sentinel() = default;
    constexpr explicit sentinel(filter_view& parent);
 
    constexpr sentinel_t<V> base() const;
 
    friend constexpr bool operator==(const iterator& x, const sentinel& y);
    friend constexpr bool operator==(const sentinel& x, const iterator& y);
    friend constexpr bool operator!=(const iterator& x, const sentinel& y);
    friend constexpr bool operator!=(const sentinel& x, const iterator& y);
  };
}

[編集] クラステンプレート std::ranges::transform_view

namespace std::ranges {
  template<InputRange V, CopyConstructible F>
    requires View<V> && is_object_v<F> &&
             RegularInvocable<F&, iter_reference_t<iterator_t<V>>>
  class transform_view : public view_interface<transform_view<V, F>> {
  private:
    // class template transform_view​::​iterator
    template<bool> struct iterator;             // exposition only
    // class template transform_view​::​sentinel
    template<bool> struct sentinel;             // exposition only
 
    V base_ = V();                              // exposition only
    semiregular_box<F> fun_;                    // exposition only
 
  public:
    transform_view() = default;
    constexpr transform_view(V base, F fun);
    template<InputRange R>
      requires ViewableRange<R> && Constructible<V, all_view<R>>
    constexpr transform_view(R&& r, F fun);
 
    constexpr V base() const;
 
    constexpr iterator<false> begin();
    constexpr iterator<true> begin() const
      requires Range<const V> &&
               RegularInvocable<const F&, iter_reference_t<iterator_t<const V>>>;
 
    constexpr sentinel<false> end();
    constexpr iterator<false> end() requires CommonRange<V>;
    constexpr sentinel<true> end() const
      requires Range<const V> &&
               RegularInvocable<const F&, iter_reference_t<iterator_t<const V>>>;
    constexpr iterator<true> end() const
      requires CommonRange<const V> &&
               RegularInvocable<const F&, iter_reference_t<iterator_t<const V>>>;
 
    constexpr auto size() requires SizedRange<V> { return ranges::size(base_); }
    constexpr auto size() const requires SizedRange<const V>
    { return ranges::size(base_); }
  };
 
  template<class R, class F>
    transform_view(R&&, F) -> transform_view<all_view<R>, F>;
}

[編集] クラステンプレート std::ranges::transform_view::iterator

namespace std::ranges {
  template<class V, class F>
  template<bool Const>
  class transform_view<V, F>::iterator {
  private:
    using Parent =                              // exposition only
      conditional_t<Const, const transform_view, transform_view>;
    using Base   =                              // exposition only
      conditional_t<Const, const V, V>;
    iterator_t<Base> current_ =                 // exposition only
      iterator_t<Base>();
    Parent* parent_ = nullptr;                  // exposition only
  public:
    using iterator_concept  = /* see definition */;
    using iterator_category = /* see definition */;
    using value_type        =
      remove_cvref_t<invoke_result_t<F&, iter_reference_t<iterator_t<Base>>>>;
    using difference_type   = iter_difference_t<iterator_t<Base>>;
 
    iterator() = default;
    constexpr iterator(Parent& parent, iterator_t<Base> current);
    constexpr iterator(iterator<!Const> i)
      requires Const && ConvertibleTo<iterator_t<V>, iterator_t<Base>>;
 
    constexpr iterator_t<Base> base() const;
    constexpr decltype(auto) operator*() const
    { return invoke(*parent_->fun_, *current_); }
 
    constexpr iterator& operator++();
    constexpr void operator++(int);
    constexpr iterator operator++(int) requires ForwardRange<Base>;
 
    constexpr iterator& operator--() requires BidirectionalRange<Base>;
    constexpr iterator operator--(int) requires BidirectionalRange<Base>;
 
    constexpr iterator& operator+=(difference_type n)
      requires RandomAccessRange<Base>;
    constexpr iterator& operator-=(difference_type n)
      requires RandomAccessRange<Base>;
    constexpr decltype(auto) operator[](difference_type n) const
      requires RandomAccessRange<Base>
    { return invoke(*parent_->fun_, current_[n]); }
 
    friend constexpr bool operator==(const iterator& x, const iterator& y)
      requires EqualityComparable<iterator_t<Base>>;
    friend constexpr bool operator!=(const iterator& x, const iterator& y)
      requires EqualityComparable<iterator_t<Base>>;
 
    friend constexpr bool operator<(const iterator& x, const iterator& y)
      requires RandomAccessRange<Base>;
    friend constexpr bool operator>(const iterator& x, const iterator& y)
      requires RandomAccessRange<Base>;
    friend constexpr bool operator<=(const iterator& x, const iterator& y)
      requires RandomAccessRange<Base>;
    friend constexpr bool operator>=(const iterator& x, const iterator& y)
      requires RandomAccessRange<Base>;
 
    friend constexpr iterator operator+(iterator i, difference_type n)
      requires RandomAccessRange<Base>;
    friend constexpr iterator operator+(difference_type n, iterator i)
      requires RandomAccessRange<Base>;
 
    friend constexpr iterator operator-(iterator i, difference_type n)
      requires RandomAccessRange<Base>;
    friend constexpr difference_type operator-(const iterator& x, const iterator& y)
      requires RandomAccessRange<Base>;
 
    friend constexpr decltype(auto) iter_move(const iterator& i)
      noexcept(noexcept(invoke(*i.parent_->fun_, *i.current_)))
    {
      if constexpr (is_lvalue_reference_v<decltype(*i)>)
        return std::move(*i);
      else
        return *i;
    }
 
    friend constexpr void iter_swap(const iterator& x, const iterator& y)
      noexcept(noexcept(ranges::iter_swap(x.current_, y.current_)))
      requires IndirectlySwappable<iterator_t<Base>>;
  };
}

[編集] クラステンプレート std::ranges::transform_view::sentinel

namespace std::ranges {
  template<class V, class F>
  template<bool Const>
  class transform_view<V, F>::sentinel {
  private:
    using Parent =                                      // exposition only
      conditional_t<Const, const transform_view, transform_view>;
    using Base = conditional_t<Const, const V, V>;      // exposition only
    sentinel_t<Base> end_ = sentinel_t<Base>();         // exposition only
  public:
    sentinel() = default;
    constexpr explicit sentinel(sentinel_t<Base> end);
    constexpr sentinel(sentinel<!Const> i)
      requires Const && ConvertibleTo<sentinel_t<V>, sentinel_t<Base>>;
 
    constexpr sentinel_t<Base> base() const;
 
    friend constexpr bool operator==(const iterator<Const>& x, const sentinel& y);
    friend constexpr bool operator==(const sentinel& x, const iterator<Const>& y);
    friend constexpr bool operator!=(const iterator<Const>& x, const sentinel& y);
    friend constexpr bool operator!=(const sentinel& x, const iterator<Const>& y);
 
    friend constexpr iter_difference_t<iterator_t<Base>>
      operator-(const iterator<Const>& x, const sentinel& y)
        requires SizedSentinel<sentinel_t<Base>, iterator_t<Base>>;
    friend constexpr iter_difference_t<iterator_t<Base>>
      operator-(const sentinel& y, const iterator<Const>& x)
        requires SizedSentinel<sentinel_t<Base>, iterator_t<Base>>;
  };
}

[編集] クラステンプレート std::ranges::take_view

namespace std::ranges {
  template<View V>
  class take_view : public view_interface<take_view<V>> {
  private:
    V base_ = V();                                      // exposition only
    iter_difference_t<iterator_t<V>> count_ = 0;        // exposition only
    // class template take_­view​::​sentinel
    template<bool> struct sentinel;                     // exposition only
  public:
    take_view() = default;
    constexpr take_view(V base, iter_difference_t<iterator_t<V>> count);
    template<ViewableRange R>
      requires Constructible<V, all_view<R>>
    constexpr take_view(R&& r, iter_difference_t<iterator_t<V>> count);
 
    constexpr V base() const;
 
    constexpr auto begin() requires (!__SimpleView<V>) {
      if constexpr (SizedRange<V>) {
        if constexpr (RandomAccessRange<V>)
          return ranges::begin(base_);
        else
          return counted_iterator{ranges::begin(base_), size()};
      } else
        return counted_iterator{ranges::begin(base_), count_};
    }
 
    constexpr auto begin() const requires Range<const V> {
      if constexpr (SizedRange<const V>) {
        if constexpr (RandomAccessRange<const V>)
          return ranges::begin(base_);
        else
          return counted_iterator{ranges::begin(base_), size()};
      } else
        return counted_iterator{ranges::begin(base_), count_};
    }
 
    constexpr auto end() requires (!__SimpleView<V>) {
      if constexpr (SizedRange<V>) {
        if constexpr (RandomAccessRange<V>)
          return ranges::begin(base_) + size();
        else
          return default_sentinel;
      } else
        return sentinel<false>{ranges::end(base_)};
    }
 
    constexpr auto end() const requires Range<const V> {
      if constexpr (SizedRange<const V>) {
        if constexpr (RandomAccessRange<const V>)
          return ranges::begin(base_) + size();
        else
          return default_sentinel;
      } else
        return sentinel<true>{ranges::end(base_)};
    }
 
    constexpr auto size() requires SizedRange<V> {
      auto n = ranges::size(base_);
      return ranges::min(n, static_cast<decltype(n)>(count_));
    }
 
    constexpr auto size() const requires SizedRange<const V> {
      auto n = ranges::size(base_);
      return ranges::min(n, static_cast<decltype(n)>(count_));
    }
  };
 
  template<Range R>
    take_view(R&&, iter_difference_t<iterator_t<R>>)
      -> take_view<all_view<R>>;
}

[編集] クラステンプレート std::ranges::take_view::sentinel

namespace std::ranges {
  template<class V>
  template<bool Const>
  class take_view<V>::sentinel {
  private:
    using Base = conditional_t<Const, const V, V>;      // exposition only
    using CI = counted_iterator<iterator_t<Base>>;      // exposition only
    sentinel_t<Base> end_ = sentinel_t<Base>();         // exposition only
  public:
    sentinel() = default;
    constexpr explicit sentinel(sentinel_t<Base> end);
    constexpr sentinel(sentinel<!Const> s)
      requires Const && ConvertibleTo<sentinel_t<V>, sentinel_t<Base>>;
 
    constexpr sentinel_t<Base> base() const;
 
    friend constexpr bool operator==(const sentinel& x, const CI& y);
    friend constexpr bool operator==(const CI& y, const sentinel& x);
    friend constexpr bool operator!=(const sentinel& x, const CI& y);
    friend constexpr bool operator!=(const CI& y, const sentinel& x);
  };
}

[編集] クラステンプレート std::ranges::join_view

namespace std::ranges {
  template<InputRange V>
    requires View<V> && InputRange<iter_reference_t<iterator_t<V>>> &&
             (is_reference_v<iter_reference_t<iterator_t<V>>> ||
              View<iter_value_t<iterator_t<V>>>)
  class join_view : public view_interface<join_view<V>> {
  private:
    using InnerRng =                    // exposition only
      iter_reference_t<iterator_t<V>>;
    // class template join_­view​::​iterator
    template<bool Const>
      struct iterator;                  // exposition only
    // class template join_­view​::​sentinel
    template<bool Const>
      struct sentinel;                  // exposition only
 
    V base_ = V();                      // exposition only
    all_view<InnerRng> inner_ =         // exposition only, present only when
      all_view<InnerRng>();              // !is_reference_v<InnerRng>
  public:
    join_view() = default;
    constexpr explicit join_view(V base);
 
    template<InputRange R>
      requires ViewableRange<R> && Constructible<V, all_view<R>>
    constexpr explicit join_view(R&& r);
 
    constexpr auto begin() {
      return iterator<__SimpleView<V>>{*this, ranges::begin(base_)};
    }
 
    constexpr auto begin() const
    requires InputRange<const V> &&
             is_reference_v<iter_reference_t<iterator_t<const V>>> {
      return iterator<true>{*this, ranges::begin(base_)};
    }
 
    constexpr auto end() {
      if constexpr (ForwardRange<V> &&
                    is_reference_v<InnerRng> && ForwardRange<InnerRng> &&
                    CommonRange<V> && CommonRange<InnerRng>)
        return iterator<__SimpleView<V>>{*this, ranges::end(base_)};
      else
        return sentinel<__SimpleView<V>>{*this};
    }
 
    constexpr auto end() const
    requires InputRange<const V> &&
             is_reference_v<iter_reference_t<iterator_t<const V>>> {
      if constexpr (ForwardRange<const V> &&
                    is_reference_v<iter_reference_t<iterator_t<const V>>> &&
                    ForwardRange<iter_reference_t<iterator_t<const V>>> &&
                    CommonRange<const V> &&
                    CommonRange<iter_reference_t<iterator_t<const V>>>)
        return iterator<true>{*this, ranges::end(base_)};
      else
        return sentinel<true>{*this};
    }
  };
 
  template<class R>
    explicit join_view(R&&) -> join_view<all_view<R>>;
}

[編集] クラステンプレート std::ranges::join_view::iterator

namespace std::ranges {
template<class V>
  template<bool Const>
  struct join_view<V>::iterator {
  private:
    using Parent =                                              // exposition only
      conditional_t<Const, const join_view, join_view>;
    using Base   = conditional_t<Const, const V, V>;            // exposition only
 
    static constexpr bool ref_is_glvalue =                      // exposition only
      is_reference_v<iter_reference_t<iterator_t<Base>>>;
 
    iterator_t<Base> outer_ = iterator_t<Base>();               // exposition only
    iterator_t<iter_reference_t<iterator_t<Base>>> inner_ =     // exposition only
      iterator_t<iter_reference_t<iterator_t<Base>>>();
    Parent* parent_ = nullptr;                                  // exposition only
 
    constexpr void satisfy();                                   // exposition only
  public:
    using iterator_concept  = /* see definition */;
    using iterator_category = /* see definition */;
    using value_type        =
      iter_value_t<iterator_t<iter_reference_t<iterator_t<Base>>>>;
    using difference_type   = /* see definition */;
 
    iterator() = default;
    constexpr iterator(Parent& parent, iterator_t<V> outer);
    constexpr iterator(iterator<!Const> i)
      requires Const &&
               ConvertibleTo<iterator_t<V>, iterator_t<Base>> &&
               ConvertibleTo<iterator_t<InnerRng>,
                             iterator_t<iter_reference_t<iterator_t<Base>>>>;
 
    constexpr decltype(auto) operator*() const { return *inner_; }
 
    constexpr iterator_t<Base> operator->() const
      requires __HasArrow<iterator_t<Base>>;
 
    constexpr iterator& operator++();
    constexpr void operator++(int);
    constexpr iterator operator++(int)
      requires ref_is_glvalue && ForwardRange<Base> &&
               ForwardRange<iter_reference_t<iterator_t<Base>>>;
 
    constexpr iterator& operator--()
      requires ref_is_glvalue && BidirectionalRange<Base> &&
               BidirectionalRange<iter_reference_t<iterator_t<Base>>>;
 
    constexpr iterator operator--(int)
      requires ref_is_glvalue && BidirectionalRange<Base> &&
               BidirectionalRange<iter_reference_t<iterator_t<Base>>>;
 
    friend constexpr bool operator==(const iterator& x, const iterator& y)
      requires ref_is_glvalue && EqualityComparable<iterator_t<Base>> &&
               EqualityComparable<iterator_t<iter_reference_t<iterator_t<Base>>>>;
 
    friend constexpr bool operator!=(const iterator& x, const iterator& y)
      requires ref_is_glvalue && EqualityComparable<iterator_t<Base>> &&
               EqualityComparable<iterator_t<iter_reference_t<iterator_t<Base>>>>;
 
    friend constexpr decltype(auto) iter_move(const iterator& i)
    noexcept(noexcept(ranges::iter_move(i.inner_))) {
      return ranges::iter_move(i.inner_);
    }
 
    friend constexpr void iter_swap(const iterator& x, const iterator& y)
      noexcept(noexcept(ranges::iter_swap(x.inner_, y.inner_)));
  };
}

[編集] クラステンプレート std::ranges::join_view::sentinel

namespace std::ranges {
  template<class V>
  template<bool Const>
  struct join_view<V>::sentinel {
  private:
    using Parent =                                      // exposition only
      conditional_t<Const, const join_view, join_view>;
    using Base   = conditional_t<Const, const V, V>;    // exposition only
    sentinel_t<Base> end_ = sentinel_t<Base>();         // exposition only
  public:
    sentinel() = default;
 
    constexpr explicit sentinel(Parent& parent);
    constexpr sentinel(sentinel<!Const> s)
      requires Const && ConvertibleTo<sentinel_t<V>, sentinel_t<Base>>;
 
    friend constexpr bool operator==(const iterator<Const>& x, const sentinel& y);
    friend constexpr bool operator==(const sentinel& x, const iterator<Const>& y);
    friend constexpr bool operator!=(const iterator<Const>& x, const sentinel& y);
    friend constexpr bool operator!=(const sentinel& x, const iterator<Const>& y);
  };
}

[編集] クラステンプレート std::ranges::split_­view

namespace std::ranges {
  template<auto> struct __require_constant;     // exposition only
 
  template<class R>
  concept __TinyRange =                         // exposition only
    SizedRange<R> &&
    requires { typename __require_constant<remove_reference_t<R>::size()>; } &&
    (remove_reference_t<R>::size() <= 1);
 
  template<InputRange V, ForwardRange Pattern>
    requires View<V> && View<Pattern> &&
             IndirectlyComparable<iterator_t<V>, iterator_t<Pattern>, ranges::equal_to> &&
             (ForwardRange<V> || __TinyRange<Pattern>)
  class split_view : public view_interface<split_view<V, Pattern>> {
  private:
    V base_ = V();                              // exposition only
    Pattern pattern_ = Pattern();               // exposition only
    iterator_t<V> current_ = iterator_t<V>();   // exposition only, present only if 
                                                // !ForwardRange<V>
    // class template split_­view​::​outer_­iterator
    template<bool> struct outer_iterator;       // exposition only
    // class template split_­view​::​inner_­iterator
    template<bool> struct inner_iterator;       // exposition only
  public:
    split_view() = default;
    constexpr split_view(V base, Pattern pattern);
 
    template<InputRange R, ForwardRange P>
      requires Constructible<V, all_view<R>> &&
               Constructible<Pattern, all_view<P>>
    constexpr split_view(R&& r, P&& p);
 
    template<InputRange R>
      requires Constructible<V, all_view<R>> &&
               Constructible<Pattern, single_view<iter_value_t<iterator_t<R>>>>
    constexpr split_view(R&& r, iter_value_t<iterator_t<R>> e);
 
    constexpr auto begin() {
      if constexpr (ForwardRange<V>)
        return outer_iterator<__SimpleView<V>>{*this, ranges::begin(base_)};
      else {
        current_ = ranges::begin(base_);
        return outer_iterator<false>{*this};
      }
    }
 
    constexpr auto begin() const requires ForwardRange<V> && ForwardRange<const V> {
      return outer_iterator<true>{*this, ranges::begin(base_)};
    }
 
    constexpr auto end() requires ForwardRange<V> && CommonRange<V> {
      return outer_iterator<__SimpleView<V>>{*this, ranges::end(base_)};
    }
 
    constexpr auto end() const {
      if constexpr (ForwardRange<V> && ForwardRange<const V> && CommonRange<const V>)
        return outer_iterator<true>{*this, ranges::end(base_)};
      else
        return default_sentinel;
    }
  };
 
  template<class R, class P>
    split_view(R&&, P&&) -> split_view<all_view<R>, all_view<P>>;
 
  template<InputRange R>
    split_view(R&&, iter_value_t<iterator_t<R>>)
      -> split_view<all_view<R>, single_view<iter_value_t<iterator_t<R>>>>;
}

[編集] クラステンプレート std::ranges::split_view::outer_iterator

namespace std::ranges {
  template<class V, class Pattern>
  template<bool Const>
  struct split_view<V, Pattern>::outer_iterator {
  private:
    using Parent =                              // exposition only
      conditional_t<Const, const split_view, split_view>;
    using Base   =                              // exposition only
      conditional_t<Const, const V, V>;
    Parent* parent_ = nullptr;                  // exposition only
    iterator_t<Base> current_ =                 // exposition only, present only
      iterator_t<Base>();                       // if V models ForwardRange
 
  public:
    using iterator_concept  =
      conditional_t<ForwardRange<Base>, forward_iterator_tag, input_iterator_tag>;
    using iterator_category = input_iterator_tag;
    struct value_type;
    using difference_type   = iter_difference_t<iterator_t<Base>>;
 
    outer_iterator() = default;
    constexpr explicit outer_iterator(Parent& parent)
      requires (!ForwardRange<Base>);
    constexpr outer_iterator(Parent& parent, iterator_t<Base> current)
      requires ForwardRange<Base>;
    constexpr outer_iterator(outer_iterator<!Const> i)
      requires Const && ConvertibleTo<iterator_t<V>, iterator_t<const V>>;
 
    constexpr value_type operator*() const;
 
    constexpr outer_iterator& operator++();
    constexpr decltype(auto) operator++(int) {
      if constexpr (ForwardRange<Base>) {
        auto tmp = *this;
        ++*this;
        return tmp;
      } else
        ++*this;
    }
 
    friend constexpr bool operator==(const outer_iterator& x, const outer_iterator& y)
      requires ForwardRange<Base>;
    friend constexpr bool operator!=(const outer_iterator& x, const outer_iterator& y)
      requires ForwardRange<Base>;
 
    friend constexpr bool operator==(const outer_iterator& x, default_sentinel_t);
    friend constexpr bool operator==(default_sentinel_t, const outer_iterator& x);
    friend constexpr bool operator!=(const outer_iterator& x, default_sentinel_t y);
    friend constexpr bool operator!=(default_sentinel_t y, const outer_iterator& x);
  };
}

[編集] クラス std::ranges::split_view::outer_iterator::value_type

namespace std::ranges {
  template<class V, class Pattern>
  template<bool Const>
  struct split_view<V, Pattern>::outer_iterator<Const>::value_type {
  private:
    outer_iterator i_ = outer_iterator();               // exposition only
  public:
    value_type() = default;
    constexpr explicit value_type(outer_iterator i);
 
    constexpr inner_iterator<Const> begin() const;
    constexpr default_sentinel_t end() const;
  };
}

[編集] クラステンプレート std::ranges::split_view::inner_iterator

namespace std::ranges {
  template<class V, class Pattern>
  template<bool Const>
  struct split_view<V, Pattern>::inner_iterator {
  private:
    using Base =
      conditional_t<Const, const V, V>;                 // exposition only
    outer_iterator<Const> i_ = outer_iterator<Const>(); // exposition only
    bool incremented_ = false;                          // exposition only
  public:
    using iterator_concept  = typename outer_iterator<Const>::iterator_concept;
    using iterator_category = /* see definition */;
    using value_type        = iter_value_t<iterator_t<Base>>;
    using difference_type   = iter_difference_t<iterator_t<Base>>;
 
    inner_iterator() = default;
    constexpr explicit inner_iterator(outer_iterator<Const> i);
 
    constexpr decltype(auto) operator*() const { return *i_.current; }
 
    constexpr inner_iterator& operator++();
    constexpr decltype(auto) operator++(int) {
      if constexpr (ForwardRange<V>) {
        auto tmp = *this;
        ++*this;
        return tmp;
      } else
        ++*this;
    }
 
    friend constexpr bool operator==(const inner_iterator& x, const inner_iterator& y)
      requires ForwardRange<Base>;
    friend constexpr bool operator!=(const inner_iterator& x, const inner_iterator& y)
      requires ForwardRange<Base>;
 
    friend constexpr bool operator==(const inner_iterator& x, default_sentinel_t);
    friend constexpr bool operator==(default_sentinel_t, const inner_iterator& x);
    friend constexpr bool operator!=(const inner_iterator& x, default_sentinel_t y);
    friend constexpr bool operator!=(default_sentinel_t y, const inner_iterator& x);
 
    friend constexpr decltype(auto) iter_move(const inner_iterator& i)
    noexcept(noexcept(ranges::iter_move(i.i_.current))) {
      return ranges::iter_move(i.i_.current);
    }
 
    friend constexpr void iter_swap(const inner_iterator& x, const inner_iterator& y)
      noexcept(noexcept(ranges::iter_swap(x.i_.current, y.i_.current)))
      requires IndirectlySwappable<iterator_t<Base>>;
  };
}

[編集] クラステンプレート std::ranges::common_view

namespace std::ranges {
  template<View V>
    requires (!CommonRange<V>)
  class common_view : public view_interface<common_view<V>> {
  private:
    V base_ = V();  // exposition only
  public:
    common_view() = default;
 
    constexpr explicit common_view(V r);
 
    template<ViewableRange R>
      requires (!CommonRange<R> && Constructible<V, all_view<R>>)
    constexpr explicit common_view(R&& r);
 
    constexpr V base() const;
 
    constexpr auto size() requires SizedRange<V> {
      return ranges::size(base_);
    }
    constexpr auto size() const requires SizedRange<const V> {
      return ranges::size(base_);
    }
 
    constexpr auto begin() {
      if constexpr (RandomAccessRange<V> && SizedRange<V>)
        return ranges::begin(base_);
      else
        return common_iterator<iterator_t<V>, sentinel_t<V>>(ranges::begin(base_));
    }
 
    constexpr auto begin() const requires Range<const V> {
      if constexpr (RandomAccessRange<const V> && SizedRange<const V>)
        return ranges::begin(base_);
      else
        return
          common_iterator<iterator_t<const V>, sentinel_t<const V>>(ranges::begin(base_));
    }
 
    constexpr auto end() {
      if constexpr (RandomAccessRange<V> && SizedRange<V>)
        return ranges::begin(base_) + ranges::size(base_);
      else
        return common_iterator<iterator_t<V>, sentinel_t<V>>(ranges::end(base_));
    }
 
    constexpr auto end() const requires Range<const V> {
      if constexpr (RandomAccessRange<const V> && SizedRange<const V>)
        return ranges::begin(base_) + ranges::size(base_);
      else
        return
          common_iterator<iterator_t<const V>, sentinel_t<const V>>(ranges::end(base_));
    }
  };
 
  template<class R>
    common_view(R&&) -> common_view<all_view<R>>;
}

[編集] クラステンプレート std::ranges::reverse_view

namespace std::ranges {
  template<View V>
    requires BidirectionalRange<V>
  class reverse_view : public view_interface<reverse_view<V>> {
  private:
    V base_ = V();  // exposition only
  public:
    reverse_view() = default;
 
    constexpr explicit reverse_view(V r);
 
    template<ViewableRange R>
      requires BidirectionalRange<R> && Constructible<V, all_view<R>>
    constexpr explicit reverse_view(R&& r);
 
    constexpr V base() const;
 
    constexpr reverse_iterator<iterator_t<V>> begin();
    constexpr reverse_iterator<iterator_t<V>> begin() requires CommonRange<V>;
    constexpr reverse_iterator<iterator_t<const V>> begin() const
      requires CommonRange<const V>;
 
    constexpr reverse_iterator<iterator_t<V>> end();
    constexpr reverse_iterator<iterator_t<const V>> end() const
      requires CommonRange<const V>;
 
    constexpr auto size() requires SizedRange<V> {
      return ranges::size(base_);
    }
    constexpr auto size() const requires SizedRange<const V> {
      return ranges::size(base_);
    }
  };
 
  template<class R>
    reverse_view(R&&) -> reverse_view<all_view<R>>;
}