24 Ranges library [ranges]

24.5 Range utilities [range.utility]

24.5.4 Sub-ranges [range.subrange]

24.5.4.1 General [range.subrange.general]

The subrange class template combines together an iterator and a sentinel into a single object that models the view concept.
Additionally, it models the sized_­range concept when the final template parameter is subrange_­kind​::​sized.
namespace std::ranges { template<class From, class To> concept uses-nonqualification-pointer-conversion = // exposition only is_pointer_v<From> && is_pointer_v<To> && !convertible_­to<remove_pointer_t<From>(*)[], remove_pointer_t<To>(*)[]>; template<class From, class To> concept convertible-to-non-slicing = // exposition only convertible_­to<From, To> && !uses-nonqualification-pointer-conversion<decay_t<From>, decay_t<To>>; template<class T> concept pair-like = // exposition only !is_reference_v<T> && requires(T t) { typename tuple_size<T>::type; // ensures tuple_­size<T> is complete requires derived_­from<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>>; { std::get<0>(t) } -> convertible_­to<const tuple_element_t<0, T>&>; { std::get<1>(t) } -> convertible_­to<const tuple_element_t<1, T>&>; }; template<class T, class U, class V> concept pair-like-convertible-from = // exposition only !range<T> && pair-like<T> && constructible_­from<T, U, V> && convertible-to-non-slicing<U, tuple_element_t<0, T>> && convertible_­to<V, tuple_element_t<1, T>>; template<input_­or_­output_­iterator I, sentinel_­for<I> S = I, subrange_kind K = sized_­sentinel_­for<S, I> ? subrange_kind::sized : subrange_kind::unsized> requires (K == subrange_kind::sized || !sized_­sentinel_­for<S, I>) class subrange : public view_interface<subrange<I, S, K>> { private: static constexpr bool StoreSize = // exposition only K == subrange_kind::sized && !sized_­sentinel_­for<S, I>; I begin_ = I(); // exposition only S end_ = S(); // exposition only make-unsigned-like-t<iter_difference_t<I>> size_ = 0; // exposition only; present only // when StoreSize is true public: subrange() requires default_­initializable<I> = default; constexpr subrange(convertible-to-non-slicing<I> auto i, S s) requires (!StoreSize); constexpr subrange(convertible-to-non-slicing<I> auto i, S s, make-unsigned-like-t<iter_difference_t<I>> n) requires (K == subrange_kind::sized); template<different-from<subrange> R> requires borrowed_­range<R> && convertible-to-non-slicing<iterator_t<R>, I> && convertible_­to<sentinel_t<R>, S> constexpr subrange(R&& r) requires (!StoreSize || sized_­range<R>); template<borrowed_­range R> requires convertible-to-non-slicing<iterator_t<R>, I> && convertible_­to<sentinel_t<R>, S> constexpr subrange(R&& r, make-unsigned-like-t<iter_difference_t<I>> n) requires (K == subrange_kind::sized) : subrange{ranges::begin(r), ranges::end(r), n} {} template<different-from<subrange> PairLike> requires pair-like-convertible-from<PairLike, const I&, const S&> constexpr operator PairLike() const; constexpr I begin() const requires copyable<I>; [[nodiscard]] constexpr I begin() requires (!copyable<I>); constexpr S end() const; constexpr bool empty() const; constexpr make-unsigned-like-t<iter_difference_t<I>> size() const requires (K == subrange_kind::sized); [[nodiscard]] constexpr subrange next(iter_difference_t<I> n = 1) const & requires forward_­iterator<I>; [[nodiscard]] constexpr subrange next(iter_difference_t<I> n = 1) &&; [[nodiscard]] constexpr subrange prev(iter_difference_t<I> n = 1) const requires bidirectional_­iterator<I>; constexpr subrange& advance(iter_difference_t<I> n); }; template<input_­or_­output_­iterator I, sentinel_­for<I> S> subrange(I, S) -> subrange<I, S>; template<input_­or_­output_­iterator I, sentinel_­for<I> S> subrange(I, S, make-unsigned-like-t<iter_difference_t<I>>) -> subrange<I, S, subrange_kind::sized>; template<borrowed_­range R> subrange(R&&) -> subrange<iterator_t<R>, sentinel_t<R>, (sized_­range<R> || sized_­sentinel_­for<sentinel_t<R>, iterator_t<R>>) ? subrange_kind::sized : subrange_kind::unsized>; template<borrowed_­range R> subrange(R&&, make-unsigned-like-t<range_difference_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 == 0 && copyable<I>) || N == 1) constexpr auto get(const subrange<I, S, K>& r); template<size_t N, class I, class S, subrange_kind K> requires (N < 2) constexpr auto get(subrange<I, S, K>&& r); } namespace std { using ranges::get; }