25 Ranges library [ranges]

25.6 Range factories [range.factories]

25.6.4 Iota view [range.iota]

25.6.4.3 Class iota_view​::​iterator [range.iota.iterator]

namespace std::ranges { template<weakly_incrementable W, semiregular Bound> requires weakly-equality-comparable-with<W, Bound> && copyable<W> struct iota_view<W, Bound>::iterator { private: W value_ = W(); // exposition only public: using iterator_concept = see below; using iterator_category = input_iterator_tag; // present only if W models incrementable and // IOTA-DIFF-T(W) is an integral type using value_type = W; using difference_type = IOTA-DIFF-T(W); iterator() requires default_initializable<W> = 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 equality_comparable<W>; friend constexpr bool operator<(const iterator& x, const iterator& y) requires totally_ordered<W>; friend constexpr bool operator>(const iterator& x, const iterator& y) requires totally_ordered<W>; friend constexpr bool operator<=(const iterator& x, const iterator& y) requires totally_ordered<W>; friend constexpr bool operator>=(const iterator& x, const iterator& y) requires totally_ordered<W>; friend constexpr auto operator<=>(const iterator& x, const iterator& y) requires totally_ordered<W> && three_way_comparable<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>; }; }
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iterator​::​iterator_concept is defined as follows:
  • (1.1)
    If W models advanceable, then iterator_concept is random_access_iterator_tag.
  • (1.2)
    Otherwise, if W models decrementable, then iterator_concept is bidirectional_iterator_tag.
  • (1.3)
    Otherwise, if W models incrementable, then iterator_concept is forward_iterator_tag.
  • (1.4)
    Otherwise, iterator_concept is input_iterator_tag.
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[Note 1: 
Overloads for iter_move and iter_swap are omitted intentionally.
— end note]
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constexpr explicit iterator(W value);
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Effects: Initializes value_ with value.
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constexpr W operator*() const noexcept(is_nothrow_copy_constructible_v<W>);
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Effects: Equivalent to: return value_;
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[Note 2: 
The noexcept clause is needed by the default iter_move implementation.
— end note]
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constexpr iterator& operator++();
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Effects: Equivalent to: ++value_; 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 incrementable<W>;
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Effects: Equivalent to: auto tmp = *this; ++*this; return tmp;
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constexpr iterator& operator--() requires decrementable<W>;
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Effects: Equivalent to: --value_; return *this;
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constexpr iterator operator--(int) requires decrementable<W>;
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Effects: Equivalent to: auto tmp = *this; --*this; return tmp;
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constexpr iterator& operator+=(difference_type n) requires advanceable<W>;
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Effects: Equivalent to: if constexpr (is-integer-like<W> && !is-signed-integer-like<W>) { if (n >= difference_type(0)) value_ += static_cast<W>(n); else value_ -= static_cast<W>(-n); } else { value_ += n; } return *this;
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constexpr iterator& operator-=(difference_type n) requires advanceable<W>;
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Effects: Equivalent to: if constexpr (is-integer-like<W> && !is-signed-integer-like<W>) { if (n >= difference_type(0)) value_ -= static_cast<W>(n); else value_ += static_cast<W>(-n); } else { value_ -= n; } return *this;
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constexpr W operator[](difference_type n) const requires advanceable<W>;
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Effects: Equivalent to: return W(value_ + n);
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friend constexpr bool operator==(const iterator& x, const iterator& y) requires equality_comparable<W>;
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Effects: Equivalent to: return x.value_ == y.value_;
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friend constexpr bool operator<(const iterator& x, const iterator& y) requires totally_ordered<W>;
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Effects: Equivalent to: return x.value_ < y.value_;
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friend constexpr bool operator>(const iterator& x, const iterator& y) requires totally_ordered<W>;
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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 totally_ordered<W>;
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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 totally_ordered<W>;
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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 totally_ordered<W> && three_way_comparable<W>;
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Effects: Equivalent to: return x.value_ <=> y.value_;
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friend constexpr iterator operator+(iterator i, difference_type n) requires advanceable<W>;
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Effects: Equivalent to: i += n; return i;
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friend constexpr iterator operator+(difference_type n, iterator i) requires advanceable<W>;
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Effects: Equivalent to: return i + n;
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friend constexpr iterator operator-(iterator i, difference_type n) requires advanceable<W>;
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Effects: Equivalent to: i -= n; return i;
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friend constexpr difference_type operator-(const iterator& x, const iterator& y) requires advanceable<W>;
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Effects: Equivalent to: using D = difference_type; if constexpr (is-integer-like<W>) { if constexpr (is-signed-integer-like<W>) return D(D(x.value_) - D(y.value_)); else return (y.value_ > x.value_) ? D(-D(y.value_ - x.value_)) : D(x.value_ - y.value_); } else { return x.value_ - y.value_; }