24 Iterators library [iterators]

24.5 Iterator adaptors [predef.iterators]

24.5.3 Constant iterators and sentinels [const.iterators]

24.5.3.3 Class template basic_const_iterator [const.iterators.iterator]

namespace std { template<class I> concept not-a-const-iterator = see below; // exposition only template<indirectly_readable I> using iter-const-rvalue-reference-t = // exposition only common_reference_t<const iter_value_t<I>&&, iter_rvalue_reference_t<I>>; template<input_iterator Iterator> class basic_const_iterator { Iterator current_ = Iterator(); // exposition only using reference = iter_const_reference_t<Iterator>; // exposition only using rvalue-reference = // exposition only iter-const-rvalue-reference-t<Iterator>; public: using iterator_concept = see below; using iterator_category = see below; // not always present using value_type = iter_value_t<Iterator>; using difference_type = iter_difference_t<Iterator>; basic_const_iterator() requires default_initializable<Iterator> = default; constexpr basic_const_iterator(Iterator current); template<convertible_to<Iterator> U> constexpr basic_const_iterator(basic_const_iterator<U> current); template<different-from<basic_const_iterator> T> requires convertible_to<T, Iterator> constexpr basic_const_iterator(T&& current); constexpr const Iterator& base() const & noexcept; constexpr Iterator base() &&; constexpr reference operator*() const; constexpr const auto* operator->() const requires is_lvalue_reference_v<iter_reference_t<Iterator>> && same_as<remove_cvref_t<iter_reference_t<Iterator>>, value_type>; constexpr basic_const_iterator& operator++(); constexpr void operator++(int); constexpr basic_const_iterator operator++(int) requires forward_iterator<Iterator>; constexpr basic_const_iterator& operator--() requires bidirectional_iterator<Iterator>; constexpr basic_const_iterator operator--(int) requires bidirectional_iterator<Iterator>; constexpr basic_const_iterator& operator+=(difference_type n) requires random_access_iterator<Iterator>; constexpr basic_const_iterator& operator-=(difference_type n) requires random_access_iterator<Iterator>; constexpr reference operator[](difference_type n) const requires random_access_iterator<Iterator>; template<sentinel_for<Iterator> S> constexpr bool operator==(const S& s) const; template<not-a-const-iterator CI> requires constant-iterator<CI> && convertible_to<Iterator const&, CI> constexpr operator CI() const &; template<not-a-const-iterator CI> requires constant-iterator<CI> && convertible_to<Iterator, CI> constexpr operator CI() &&; constexpr bool operator<(const basic_const_iterator& y) const requires random_access_iterator<Iterator>; constexpr bool operator>(const basic_const_iterator& y) const requires random_access_iterator<Iterator>; constexpr bool operator<=(const basic_const_iterator& y) const requires random_access_iterator<Iterator>; constexpr bool operator>=(const basic_const_iterator& y) const requires random_access_iterator<Iterator>; constexpr auto operator<=>(const basic_const_iterator& y) const requires random_access_iterator<Iterator> && three_way_comparable<Iterator>; template<different-from<basic_const_iterator> I> constexpr bool operator<(const I& y) const requires random_access_iterator<Iterator> && totally_ordered_with<Iterator, I>; template<different-from<basic_const_iterator> I> constexpr bool operator>(const I& y) const requires random_access_iterator<Iterator> && totally_ordered_with<Iterator, I>; template<different-from<basic_const_iterator> I> constexpr bool operator<=(const I& y) const requires random_access_iterator<Iterator> && totally_ordered_with<Iterator, I>; template<different-from<basic_const_iterator> I> constexpr bool operator>=(const I& y) const requires random_access_iterator<Iterator> && totally_ordered_with<Iterator, I>; template<different-from<basic_const_iterator> I> constexpr auto operator<=>(const I& y) const requires random_access_iterator<Iterator> && totally_ordered_with<Iterator, I> && three_way_comparable_with<Iterator, I>; template<not-a-const-iterator I> friend constexpr bool operator<(const I& x, const basic_const_iterator& y) requires random_access_iterator<Iterator> && totally_ordered_with<Iterator, I>; template<not-a-const-iterator I> friend constexpr bool operator>(const I& x, const basic_const_iterator& y) requires random_access_iterator<Iterator> && totally_ordered_with<Iterator, I>; template<not-a-const-iterator I> friend constexpr bool operator<=(const I& x, const basic_const_iterator& y) requires random_access_iterator<Iterator> && totally_ordered_with<Iterator, I>; template<not-a-const-iterator I> friend constexpr bool operator>=(const I& x, const basic_const_iterator& y) requires random_access_iterator<Iterator> && totally_ordered_with<Iterator, I>; friend constexpr basic_const_iterator operator+(const basic_const_iterator& i, difference_type n) requires random_access_iterator<Iterator>; friend constexpr basic_const_iterator operator+(difference_type n, const basic_const_iterator& i) requires random_access_iterator<Iterator>; friend constexpr basic_const_iterator operator-(const basic_const_iterator& i, difference_type n) requires random_access_iterator<Iterator>; template<sized_sentinel_for<Iterator> S> constexpr difference_type operator-(const S& y) const; template<not-a-const-iterator S> requires sized_sentinel_for<S, Iterator> friend constexpr difference_type operator-(const S& x, const basic_const_iterator& y); friend constexpr rvalue-reference iter_move(const basic_const_iterator& i) noexcept(noexcept(static_cast<rvalue-reference>(ranges::iter_move(i.current_)))) { return static_cast<rvalue-reference>(ranges::iter_move(i.current_)); } }; }

Given some type I, the concept not-a-const-iterator is defined as false if I is a specialization of basic_const_iterator and true otherwise.