25 Ranges library [ranges]

25.7 Range adaptors [range.adaptors]

25.7.25 Zip view [range.zip]

25.7.25.3 Class template zip_view​::​iterator [range.zip.iterator]

namespace std::ranges { template<input_range... Views> requires (view<Views> && ...) && (sizeof...(Views) > 0) template<bool Const> class zip_view<Views...>::iterator { tuple<iterator_t<maybe-const<Const, Views>>...> current_; // exposition only constexpr explicit iterator(tuple<iterator_t<maybe-const<Const, Views>>...>); // exposition only public: using iterator_category = input_iterator_tag; // not always present using iterator_concept = see below; using value_type = tuple<range_value_t<maybe-const<Const, Views>>...>; using difference_type = common_type_t<range_difference_t<maybe-const<Const, Views>>...>; iterator() = default; constexpr iterator(iterator<!Const> i) requires Const && (convertible_to<iterator_t<Views>, iterator_t<const Views>> && ...); constexpr auto operator*() const; constexpr iterator& operator++(); constexpr void operator++(int); constexpr iterator operator++(int) requires all-forward<Const, Views...>; constexpr iterator& operator--() requires all-bidirectional<Const, Views...>; constexpr iterator operator--(int) requires all-bidirectional<Const, Views...>; constexpr iterator& operator+=(difference_type x) requires all-random-access<Const, Views...>; constexpr iterator& operator-=(difference_type x) requires all-random-access<Const, Views...>; constexpr auto operator[](difference_type n) const requires all-random-access<Const, Views...>; friend constexpr bool operator==(const iterator& x, const iterator& y) requires (equality_comparable<iterator_t<maybe-const<Const, Views>>> && ...); friend constexpr auto operator<=>(const iterator& x, const iterator& y) requires all-random-access<Const, Views...>; friend constexpr iterator operator+(const iterator& i, difference_type n) requires all-random-access<Const, Views...>; friend constexpr iterator operator+(difference_type n, const iterator& i) requires all-random-access<Const, Views...>; friend constexpr iterator operator-(const iterator& i, difference_type n) requires all-random-access<Const, Views...>; friend constexpr difference_type operator-(const iterator& x, const iterator& y) requires (sized_sentinel_for<iterator_t<maybe-const<Const, Views>>, iterator_t<maybe-const<Const, Views>>> && ...); friend constexpr auto iter_move(const iterator& i) noexcept(see below); friend constexpr void iter_swap(const iterator& l, const iterator& r) noexcept(see below) requires (indirectly_swappable<iterator_t<maybe-const<Const, Views>>> && ...); }; }
1
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iterator​::​iterator_concept is defined as follows:
  • (1.1)
    If all-random-access<Const, Views...> is modeled, then iterator_concept denotes random_access_iterator_tag.
  • (1.2)
    Otherwise, if all-bidirectional<Const, Views...> is modeled, then iterator_concept denotes bidirectional_iterator_tag.
  • (1.3)
    Otherwise, if all-forward<Const, Views...> is modeled, then iterator_concept denotes forward_iterator_tag.
  • (1.4)
    Otherwise, iterator_concept denotes input_iterator_tag.
2
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iterator​::​iterator_category is present if and only if all-forward<Const, Views...> is modeled.
3
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If the invocation of any non-const member function of iterator exits via an exception, the iterator acquires a singular value.
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constexpr explicit iterator(tuple<iterator_t<maybe-const<Const, Views>>...> current);
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Effects: Initializes current_ with std​::​move(current).
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constexpr iterator(iterator<!Const> i) requires Const && (convertible_to<iterator_t<Views>, iterator_t<const Views>> && ...);
5
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Effects: Initializes current_ with std​::​move(i.current_).
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constexpr auto operator*() const;
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Effects: Equivalent to: return tuple-transform([](auto& i) -> decltype(auto) { return *i; }, current_);
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constexpr iterator& operator++();
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Effects: Equivalent to: tuple-for-each([](auto& i) { ++i; }, current_); return *this;
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constexpr void operator++(int);
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Effects: Equivalent to ++*this.
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constexpr iterator operator++(int) requires all-forward<Const, Views...>;
9
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Effects: Equivalent to: auto tmp = *this; ++*this; return tmp;
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constexpr iterator& operator--() requires all-bidirectional<Const, Views...>;
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Effects: Equivalent to: tuple-for-each([](auto& i) { --i; }, current_); return *this;
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constexpr iterator operator--(int) requires all-bidirectional<Const, Views...>;
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Effects: Equivalent to: auto tmp = *this; --*this; return tmp;
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constexpr iterator& operator+=(difference_type x) requires all-random-access<Const, Views...>;
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Effects: Equivalent to: tuple-for-each([&]<class I>(I& i) { i += iter_difference_t<I>(x); }, current_); return *this;
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constexpr iterator& operator-=(difference_type x) requires all-random-access<Const, Views...>;
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Effects: Equivalent to: tuple-for-each([&]<class I>(I& i) { i -= iter_difference_t<I>(x); }, current_); return *this;
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constexpr auto operator[](difference_type n) const requires all-random-access<Const, Views...>;
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Effects: Equivalent to: return tuple-transform([&]<class I>(I& i) -> decltype(auto) { return i[iter_difference_t<I>(n)]; }, current_);
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friend constexpr bool operator==(const iterator& x, const iterator& y) requires (equality_comparable<iterator_t<maybe-const<Const, Views>>> && ...);
15
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Returns:
  • (15.1)
    x.current_ == y.current_ if all-bidirectional<Const, Views...> is true.
  • (15.2)
    Otherwise, true if there exists an integer such that bool(std​::​​get<i>(x.current_) == std​::​get<i>(y.current_)) is true.
    [Note 1: 
    This allows zip_view to model common_range when all constituent views model common_range.
    — end note]
  • (15.3)
    Otherwise, false.
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friend constexpr auto operator<=>(const iterator& x, const iterator& y) requires all-random-access<Const, Views...>;
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Returns: x.current_ <=> y.current_.
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friend constexpr iterator operator+(const iterator& i, difference_type n) requires all-random-access<Const, Views...>; friend constexpr iterator operator+(difference_type n, const iterator& i) requires all-random-access<Const, Views...>;
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Effects: Equivalent to: auto r = i; r += n; return r;
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friend constexpr iterator operator-(const iterator& i, difference_type n) requires all-random-access<Const, Views...>;
18
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Effects: Equivalent to: auto r = i; r -= n; return r;
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friend constexpr difference_type operator-(const iterator& x, const iterator& y) requires (sized_sentinel_for<iterator_t<maybe-const<Const, Views>>, iterator_t<maybe-const<Const, Views>>> && ...);
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Let DIST(i) be difference_type(std​::​get<i>(x.current_) - std​::​get<i>(y.current_)).
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Returns: The value with the smallest absolute value among DIST(n) for all integers .
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friend constexpr auto iter_move(const iterator& i) noexcept(see below);
21
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Effects: Equivalent to: return tuple-transform(ranges::iter_move, i.current_);
22
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Remarks: The exception specification is equivalent to: (noexcept(ranges::iter_move(declval<const iterator_t<maybe-const<Const, Views>>&>())) && ...) && (is_nothrow_move_constructible_v<range_rvalue_reference_t<maybe-const<Const, Views>>> && ...)
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friend constexpr void iter_swap(const iterator& l, const iterator& r) noexcept(see below) requires (indirectly_swappable<iterator_t<maybe-const<Const, Views>>> && ...);
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Effects: For every integer , performs: ranges::iter_swap(std::get<i>(l.current_), std::get<i>(r.current_))
24
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Remarks: The exception specification is equivalent to the logical and of the following expressions: noexcept(ranges::iter_swap(std::get<i>(l.current_), std::get<i>(r.current_))) for every integer .