25 Ranges library [ranges]

25.7 Range adaptors [range.adaptors]

25.7.32 Stride view [range.stride]

25.7.32.3 Class template stride_view​::​iterator [range.stride.iterator]

namespace std::ranges { template<input_range V> requires view<V> template<bool Const> class stride_view<V>::iterator { using Parent = maybe-const<Const, stride_view>; // exposition only using Base = maybe-const<Const, V>; // exposition only iterator_t<Base> current_ = iterator_t<Base>(); // exposition only sentinel_t<Base> end_ = sentinel_t<Base>(); // exposition only range_difference_t<Base> stride_ = 0; // exposition only range_difference_t<Base> missing_ = 0; // exposition only constexpr iterator(Parent* parent, iterator_t<Base> current, // exposition only range_difference_t<Base> missing = 0); public: using difference_type = range_difference_t<Base>; using value_type = range_value_t<Base>; using iterator_concept = see below; using iterator_category = see below; // not always present iterator() requires default_initializable<iterator_t<Base>> = default; constexpr iterator(iterator<!Const> other) requires Const && convertible_to<iterator_t<V>, iterator_t<Base>> && convertible_to<sentinel_t<V>, sentinel_t<Base>>; constexpr iterator_t<Base> base() &&; constexpr const iterator_t<Base>& base() const & noexcept; constexpr decltype(auto) operator*() const { return *current_; } constexpr iterator& operator++(); constexpr void operator++(int); constexpr iterator operator++(int) requires forward_range<Base>; constexpr iterator& operator--() requires bidirectional_range<Base>; constexpr iterator operator--(int) requires bidirectional_range<Base>; constexpr iterator& operator+=(difference_type n) requires random_access_range<Base>; constexpr iterator& operator-=(difference_type n) requires random_access_range<Base>; constexpr decltype(auto) operator[](difference_type n) const requires random_access_range<Base> { return *(*this + n); } friend constexpr bool operator==(const iterator& x, default_sentinel_t); friend constexpr bool operator==(const iterator& x, const iterator& y) requires equality_comparable<iterator_t<Base>>; friend constexpr bool operator<(const iterator& x, const iterator& y) requires random_access_range<Base>; friend constexpr bool operator>(const iterator& x, const iterator& y) requires random_access_range<Base>; friend constexpr bool operator<=(const iterator& x, const iterator& y) requires random_access_range<Base>; friend constexpr bool operator>=(const iterator& x, const iterator& y) requires random_access_range<Base>; friend constexpr auto operator<=>(const iterator& x, const iterator& y) requires random_access_range<Base> && three_way_comparable<iterator_t<Base>>; friend constexpr iterator operator+(const iterator& x, difference_type n) requires random_access_range<Base>; friend constexpr iterator operator+(difference_type n, const iterator& x) requires random_access_range<Base>; friend constexpr iterator operator-(const iterator& x, difference_type n) requires random_access_range<Base>; friend constexpr difference_type operator-(const iterator& x, const iterator& y) requires sized_sentinel_for<iterator_t<Base>, iterator_t<Base>>; friend constexpr difference_type operator-(default_sentinel_t y, const iterator& x) requires sized_sentinel_for<sentinel_t<Base>, iterator_t<Base>>; friend constexpr difference_type operator-(const iterator& x, default_sentinel_t y) requires sized_sentinel_for<sentinel_t<Base>, iterator_t<Base>>; friend constexpr range_rvalue_reference_t<Base> 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 indirectly_swappable<iterator_t<Base>>; }; }
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iterator​::​iterator_concept is defined as follows:
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The member typedef-name iterator_category is defined if and only if Base models forward_range.
In that case, iterator​::​iterator_category is defined as follows:
  • (2.1)
    Let C denote the type iterator_traits<iterator_t<Base>>​::​iterator_category.
  • (2.2)
    If C models derived_from<random_access_iterator_tag>, then iterator_category denotes random_access_iterator_tag.
  • (2.3)
    Otherwise, iterator_category denotes C.
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constexpr iterator(Parent* parent, iterator_t<Base> current, range_difference_t<Base> missing = 0);
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Effects: Initializes current_ with std​::​move(current), end_ with ranges​::​end(parent->base_), stride_ with parent->stride_, and missing_ with missing.
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constexpr iterator(iterator<!Const> i) requires Const && convertible_to<iterator_t<V>, iterator_t<Base>> && convertible_to<sentinel_t<V>, sentinel_t<Base>>;
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Effects: Initializes current_ with std​::​move(i.current_), end_ with std​::​move(i.end_), stride_ with i.stride_, and missing_ with i.missing_.
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constexpr iterator_t<Base> base() &&;
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Returns: std​::​move(current_).
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constexpr const iterator_t<Base>& base() const & noexcept;
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Returns: current_.
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constexpr iterator& operator++();
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Preconditions: current_ != end_ is true.
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Effects: Equivalent to: missing_ = ranges::advance(current_, stride_, end_); 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 forward_range<Base>;
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Effects: Equivalent to: auto tmp = *this; ++*this; return tmp;
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constexpr iterator& operator--() requires bidirectional_range<Base>;
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Effects: Equivalent to: ranges::advance(current_, missing_ - stride_); missing_ = 0; return *this;
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constexpr iterator operator--(int) requires bidirectional_range<Base>;
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Effects: Equivalent to: auto tmp = *this; --*this; return tmp;
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constexpr iterator& operator+=(difference_type n) requires random_access_range<Base>;
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Preconditions: If n is positive, ranges​::​distance(current_, end_) > stride_ * (n - 1) is true.
[Note 1: 
If n is negative, the Effects paragraph implies a precondition.
— end note]
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Effects: Equivalent to: if (n > 0) { ranges::advance(current_, stride_ * (n - 1)); missing_ = ranges::advance(current_, stride_, end_); } else if (n < 0) { ranges::advance(current_, stride_ * n + missing_); missing_ = 0; } return *this;
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constexpr iterator& operator-=(difference_type x) requires random_access_range<Base>;
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Effects: Equivalent to: return *this += -x;
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friend constexpr bool operator==(const iterator& x, default_sentinel_t);
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Returns: x.current_ == x.end_.
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friend constexpr bool operator==(const iterator& x, const iterator& y) requires equality_comparable<iterator_t<Base>>;
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Returns: x.current_ == y.current_.
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friend constexpr bool operator<(const iterator& x, const iterator& y) requires random_access_range<Base>;
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Returns: x.current_ < y.current_.
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friend constexpr bool operator>(const iterator& x, const iterator& y) requires random_access_range<Base>;
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Effects: Equivalent to: return y < x;
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friend constexpr bool operator<=(const iterator& x, const iterator& y) requires random_access_range<Base>;
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Effects: Equivalent to: return !(y < x);
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friend constexpr bool operator>=(const iterator& x, const iterator& y) requires random_access_range<Base>;
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Effects: Equivalent to: return !(x < y);
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friend constexpr auto operator<=>(const iterator& x, const iterator& y) requires random_access_range<Base> && three_way_comparable<iterator_t<Base>>;
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Returns: x.current_ <=> y.current_.
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friend constexpr iterator operator+(const iterator& i, difference_type n) requires random_access_range<Base>; friend constexpr iterator operator+(difference_type n, const iterator& i) requires random_access_range<Base>;
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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 random_access_range<Base>;
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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<Base>, iterator_t<Base>>;
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Returns: Let N be (x.current_ - y.current_).
  • (25.1)
    If Base models forward_range, (N + x.missing_ - y.missing_) / x.stride_.
  • (25.2)
    Otherwise, if N is negative, -div-ceil(-N, x.stride_).
  • (25.3)
    Otherwise, div-ceil(N, x.stride_).
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friend constexpr difference_type operator-(default_sentinel_t y, const iterator& x) requires sized_sentinel_for<sentinel_t<Base>, iterator_t<Base>>;
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Returns: div-ceil(x.end_ - x.current_, x.stride_).
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friend constexpr difference_type operator-(const iterator& x, default_sentinel_t y) requires sized_sentinel_for<sentinel_t<Base>, iterator_t<Base>>;
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Effects: Equivalent to: return -(y - x);
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friend constexpr range_rvalue_reference_t<Base> iter_move(const iterator& i) noexcept(noexcept(ranges::iter_move(i.current_)));
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Effects: Equivalent to: return ranges​::​iter_move(i.current_);
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friend constexpr void iter_swap(const iterator& x, const iterator& y) noexcept(noexcept(ranges::iter_swap(x.current_, y.current_))) requires indirectly_swappable<iterator_t<Base>>;
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Effects: Equivalent to: ranges​::​iter_swap(x.current_, y.current_);