[range.subrange] (original) (raw)
25 Ranges library [ranges]
25.5 Range utilities [range.utility]
25.5.4 Sub-ranges [range.subrange]
25.5.4.1 General [range.subrange.general]
25.5.4.2 Constructors and conversions [range.subrange.ctor]
25.5.4.3 Accessors [range.subrange.access]
25.5.4.1 General [range.subrange.general]
The subrange class template combines together an iterator and a sentinel into a single object that models theview concept.
Additionally, it models thesized_range concept when the final template parameter issubrange_kind::sized.
namespace std::ranges { template<class From, class To> concept uses-nonqualification-pointer-conversion = is_pointer_v<From> && is_pointer_v<To> && <remove_pointer_t<From>(*)[], remove_pointer_t<To>(*)[]>;template<class From, class To> concept convertible-to-non-slicing = convertible_to<From, To> &&
<decay_t<From>, decay_t<To>>;template<class T, class U, class V> concept pair-like-convertible-from =
<T> && !is_reference_v<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 ||
<S, I>) class subrange : public view_interface<subrange<I, S, K>> { private: static constexpr bool StoreSize = K == subrange_kind::sized &&
<S, I>; I begin_ = I(); S end_ = S(); make-unsigned-like-t<iter_difference_t<I>> size_ = 0; 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>;constexpr I begin() requires (
<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);constexpr subrange next(iter_difference_t<I> n = 1) const & requires forward_iterator<I>;constexpr subrange next(iter_difference_t<I> n = 1) &&;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>;}
25.5.4.2 Constructors and conversions [range.subrange.ctor]
constexpr subrange([_convertible-to-non-slicing_](#concept:convertible-to-non-slicing "25.5.4.1 General [range.subrange.general]")<I> auto i, S s) requires (!_StoreSize_);
Preconditions: [i, s) is a valid range.
Effects: Initializes begin_ with std::move(i) and end_ withs.
constexpr subrange([_convertible-to-non-slicing_](#concept:convertible-to-non-slicing "25.5.4.1 General [range.subrange.general]")<I> auto i, S s,_make-unsigned-like-t_<iter_difference_t<I>> n) requires (K == subrange_kind::sized);
Preconditions: [i, s) is a valid range, andn == _to-unsigned-like_(ranges::distance(i, s))is true.
Effects: Initializes begin_ with std::move(i) and end_ withs.
If StoreSize is true, initializes size_ withn.
[Note 1:
Accepting the length of the range and storing it to later return fromsize() enables subrange to model sized_range even when it stores an iterator and sentinel that do not modelsized_sentinel_for.
— _end note_]
Effects: Equivalent to:
- If StoreSize is true,subrange(r, static_cast<decltype(_size__)>(ranges::size(r))).
- Otherwise, subrange(ranges::begin(r), ranges::end(r)).
template<[_different-from_](range.utility.helpers#concept:different-from "25.5.2 Helper concepts [range.utility.helpers]")<subrange> PairLike> requires [_pair-like-convertible-from_](#concept:pair-like-convertible-from "25.5.4.1 General [range.subrange.general]")<PairLike, const I&, const S&> constexpr operator PairLike() const;
Effects: Equivalent to: return PairLike(begin_, end_);
25.5.4.3 Accessors [range.subrange.access]
constexpr I begin() const requires [copyable](concepts.object#concept:copyable "18.6 Object concepts [concepts.object]")<I>;
Effects: Equivalent to: return begin_;
constexpr I begin() requires (<I>);
Effects: Equivalent to: return std::move(begin_);
Effects: Equivalent to: return end_;
constexpr bool empty() const;
Effects: Equivalent to: return begin_ == end_;
constexpr _make-unsigned-like-t_<iter_difference_t<I>> size() const requires (K == subrange_kind::sized);
Effects:
- If StoreSize is true, equivalent to: return size_;
- Otherwise, equivalent to: return to-unsigned-like(end_ - begin_);
constexpr subrange next(iter_difference_t<I> n = 1) const & requires [forward_iterator](iterator.concept.forward#concept:forward%5Fiterator "24.3.4.11 Concept forward_iterator [iterator.concept.forward]")<I>;
Effects: Equivalent to:auto tmp = *this; tmp.advance(n);return tmp;
constexpr subrange next(iter_difference_t<I> n = 1) &&;
Effects: Equivalent to:advance(n);return std::move(*this);
Effects: Equivalent to:auto tmp = *this; tmp.advance(-n);return tmp;
constexpr subrange& advance(iter_difference_t<I> n);
Effects: Equivalent to:if constexpr (bidirectional_iterator<I>) { if (n < 0) { ranges::advance(begin_, n);if constexpr (StoreSize) size_ += to-unsigned-like(-n);return *this;} } auto d = n - ranges::advance(begin_, n, end_);if constexpr (StoreSize) size_ -= to-unsigned-like(d);return *this;
template<size_t N, class I, class S, subrange_kind K> requires ((N == 0 && [copyable](concepts.object#concept:copyable "18.6 Object concepts [concepts.object]")<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);
Effects: Equivalent to:if constexpr (N == 0) return r.begin();else return r.end();