23 Containers library [containers]

23.3 Sequence containers [sequences]

23.3.1 General [sequences.general]

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The headers <array>, <deque>, <forward_list>, <hive>, <inplace_vector>, <list>, and <vector> define class templates that meet the requirements for sequence containers.
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The following exposition-only alias template may appear in deduction guides for sequence containers: template<class InputIterator> using iter-value-type = typename iterator_traits<InputIterator>::value_type; // exposition only

23.3.2 Header <array> synopsis [array.syn]

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// mostly freestanding #include <compare> // see [compare.syn] #include <initializer_list> // see [initializer.list.syn] namespace std { // [array], class template array template<class T, size_t N> struct array; // partially freestanding template<class T, size_t N> constexpr bool operator==(const array<T, N>& x, const array<T, N>& y); template<class T, size_t N> constexpr synth-three-way-result<T> operator<=>(const array<T, N>& x, const array<T, N>& y); // [array.special], specialized algorithms template<class T, size_t N> constexpr void swap(array<T, N>& x, array<T, N>& y) noexcept(noexcept(x.swap(y))); // [array.creation], array creation functions template<class T, size_t N> constexpr array<remove_cv_t<T>, N> to_array(T (&a)[N]); template<class T, size_t N> constexpr array<remove_cv_t<T>, N> to_array(T (&&a)[N]); // [array.tuple], tuple interface template<class T> struct tuple_size; template<size_t I, class T> struct tuple_element; template<class T, size_t N> struct tuple_size<array<T, N>>; template<size_t I, class T, size_t N> struct tuple_element<I, array<T, N>>; template<size_t I, class T, size_t N> constexpr T& get(array<T, N>&) noexcept; template<size_t I, class T, size_t N> constexpr T&& get(array<T, N>&&) noexcept; template<size_t I, class T, size_t N> constexpr const T& get(const array<T, N>&) noexcept; template<size_t I, class T, size_t N> constexpr const T&& get(const array<T, N>&&) noexcept; }

23.3.3 Class template array [array]

23.3.3.1 Overview [array.overview]

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The header <array> defines a class template for storing fixed-size sequences of objects.
An array is a contiguous container.
An instance of array<T, N> stores N elements of type T, so that size() == N is an invariant.
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An array is an aggregate that can be list-initialized with up to N elements whose types are convertible to T.
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An array meets all of the requirements of a container ([container.reqmts]) and of a reversible container ([container.rev.reqmts]), except that a default constructed array object is not empty if .
An array meets some of the requirements of a sequence container.
Descriptions are provided here only for operations on array that are not described in one of these tables and for operations where there is additional semantic information.
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array<T, N> is a structural type ([temp.param]) if T is a structural type.
Two values a1 and a2 of type array<T, N> are template-argument-equivalent if and only if each pair of corresponding elements in a1 and a2 are template-argument-equivalent.
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The types iterator and const_iterator meet the constexpr iterator requirements.
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namespace std { template<class T, size_t N> struct array { // types using value_type = T; using pointer = T*; using const_pointer = const T*; using reference = T&; using const_reference = const T&; using size_type = size_t; using difference_type = ptrdiff_t; using iterator = implementation-defined; // see [container.requirements] using const_iterator = implementation-defined; // see [container.requirements] using reverse_iterator = std::reverse_iterator<iterator>; using const_reverse_iterator = std::reverse_iterator<const_iterator>; // no explicit construct/copy/destroy for aggregate type constexpr void fill(const T& u); constexpr void swap(array&) noexcept(is_nothrow_swappable_v<T>); // iterators constexpr iterator begin() noexcept; constexpr const_iterator begin() const noexcept; constexpr iterator end() noexcept; constexpr const_iterator end() const noexcept; constexpr reverse_iterator rbegin() noexcept; constexpr const_reverse_iterator rbegin() const noexcept; constexpr reverse_iterator rend() noexcept; constexpr const_reverse_iterator rend() const noexcept; constexpr const_iterator cbegin() const noexcept; constexpr const_iterator cend() const noexcept; constexpr const_reverse_iterator crbegin() const noexcept; constexpr const_reverse_iterator crend() const noexcept; // capacity constexpr bool empty() const noexcept; constexpr size_type size() const noexcept; constexpr size_type max_size() const noexcept; // element access constexpr reference operator[](size_type n); constexpr const_reference operator[](size_type n) const; constexpr reference at(size_type n); // freestanding-deleted constexpr const_reference at(size_type n) const; // freestanding-deleted constexpr reference front(); constexpr const_reference front() const; constexpr reference back(); constexpr const_reference back() const; constexpr T* data() noexcept; constexpr const T* data() const noexcept; }; template<class T, class... U> array(T, U...) -> array<T, 1 + sizeof...(U)>; }

23.3.3.2 Constructors, copy, and assignment [array.cons]

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An array relies on the implicitly-declared special member functions ([class.default.ctor], [class.dtor], [class.copy.ctor]) to conform to the container requirements table in [container.requirements].
In addition to the requirements specified in the container requirements table, the implicitly-declared move constructor and move assignment operator for array require that T be Cpp17MoveConstructible or Cpp17MoveAssignable, respectively.
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template<class T, class... U> array(T, U...) -> array<T, 1 + sizeof...(U)>;
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Mandates: (is_same_v<T, U> && ...) is true.

23.3.3.3 Member functions [array.members]

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constexpr size_type size() const noexcept;
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Returns: N.
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constexpr T* data() noexcept; constexpr const T* data() const noexcept;
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Returns: A pointer such that [data(), data() + size()) is a valid range.
For a non-empty array, data() == addressof(front()) is true.
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constexpr void fill(const T& u);
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Effects: As if by fill_n(begin(), N, u).
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constexpr void swap(array& y) noexcept(is_nothrow_swappable_v<T>);
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Effects: Equivalent to swap_ranges(begin(), end(), y.begin()).
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[Note 1: 
Unlike the swap function for other containers, array​::​swap takes linear time, can exit via an exception, and does not cause iterators to become associated with the other container.
— end note]

23.3.3.4 Specialized algorithms [array.special]

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template<class T, size_t N> constexpr void swap(array<T, N>& x, array<T, N>& y) noexcept(noexcept(x.swap(y)));
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Constraints: N == 0 or is_swappable_v<T> is true.
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Effects: As if by x.swap(y).
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Complexity: Linear in N.

23.3.3.5 Zero-sized arrays [array.zero]

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array shall provide support for the special case N == 0.
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In the case that N == 0, begin() == end() == unique value.
The return value of data() is unspecified.
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The effect of calling front() or back() for a zero-sized array is undefined.
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Member function swap() shall have a non-throwing exception specification.

23.3.3.6 Array creation functions [array.creation]

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template<class T, size_t N> constexpr array<remove_cv_t<T>, N> to_array(T (&a)[N]);
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Mandates: is_array_v<T> is false and is_constructible_v<remove_cv_t<T>, T&> is true.
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Preconditions: T meets the Cpp17CopyConstructible requirements.
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Returns: {{ a[0], …, a[N - 1] }}.
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template<class T, size_t N> constexpr array<remove_cv_t<T>, N> to_array(T (&&a)[N]);
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Mandates: is_array_v<T> is false and is_constructible_v<remove_cv_t<T>, T> is true.
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Preconditions: T meets the Cpp17MoveConstructible requirements.
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Returns: {{ std​::​move(a[0]), …, std​::​move(a[N - 1]) }}.

23.3.3.7 Tuple interface [array.tuple]

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template<class T, size_t N> struct tuple_size<array<T, N>> : integral_constant<size_t, N> { };
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template<size_t I, class T, size_t N> struct tuple_element<I, array<T, N>> { using type = T; };
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Mandates: I < N is true.
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template<size_t I, class T, size_t N> constexpr T& get(array<T, N>& a) noexcept; template<size_t I, class T, size_t N> constexpr T&& get(array<T, N>&& a) noexcept; template<size_t I, class T, size_t N> constexpr const T& get(const array<T, N>& a) noexcept; template<size_t I, class T, size_t N> constexpr const T&& get(const array<T, N>&& a) noexcept;
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Mandates: I < N is true.
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Returns: A reference to the element of a, where indexing is zero-based.

23.3.4 Header <deque> synopsis [deque.syn]

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#include <compare> // see [compare.syn] #include <initializer_list> // see [initializer.list.syn] namespace std { // [deque], class template deque template<class T, class Allocator = allocator<T>> class deque; template<class T, class Allocator> constexpr bool operator==(const deque<T, Allocator>& x, const deque<T, Allocator>& y); template<class T, class Allocator> constexpr synth-three-way-result<T> operator<=>(const deque<T, Allocator>& x, const deque<T, Allocator>& y); template<class T, class Allocator> constexpr void swap(deque<T, Allocator>& x, deque<T, Allocator>& y) noexcept(noexcept(x.swap(y))); // [deque.erasure], erasure template<class T, class Allocator, class U = T> constexpr typename deque<T, Allocator>::size_type erase(deque<T, Allocator>& c, const U& value); template<class T, class Allocator, class Predicate> constexpr typename deque<T, Allocator>::size_type erase_if(deque<T, Allocator>& c, Predicate pred); namespace pmr { template<class T> using deque = std::deque<T, polymorphic_allocator<T>>; } }

23.3.5 Class template deque [deque]

23.3.5.1 Overview [deque.overview]

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A deque is a sequence container that supports random access iterators.
In addition, it supports constant time insert and erase operations at the beginning or the end; insert and erase in the middle take linear time.
That is, a deque is especially optimized for pushing and popping elements at the beginning and end.
Storage management is handled automatically.
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A deque meets all of the requirements of a container ([container.reqmts]), of a reversible container ([container.rev.reqmts]), of an allocator-aware container ([container.alloc.reqmts]), and of a sequence container, including the optional sequence container requirements ([sequence.reqmts]).
Descriptions are provided here only for operations on deque that are not described in one of these tables or for operations where there is additional semantic information.
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The types iterator and const_iterator meet the constexpr iterator requirements ([iterator.requirements.general]).
namespace std { template<class T, class Allocator = allocator<T>> class deque { public: // types using value_type = T; using allocator_type = Allocator; using pointer = typename allocator_traits<Allocator>::pointer; using const_pointer = typename allocator_traits<Allocator>::const_pointer; using reference = value_type&; using const_reference = const value_type&; using size_type = implementation-defined; // see [container.requirements] using difference_type = implementation-defined; // see [container.requirements] using iterator = implementation-defined; // see [container.requirements] using const_iterator = implementation-defined; // see [container.requirements] using reverse_iterator = std::reverse_iterator<iterator>; using const_reverse_iterator = std::reverse_iterator<const_iterator>; // [deque.cons], construct/copy/destroy constexpr deque() : deque(Allocator()) { } constexpr explicit deque(const Allocator&); constexpr explicit deque(size_type n, const Allocator& = Allocator()); constexpr deque(size_type n, const T& value, const Allocator& = Allocator()); template<class InputIterator> constexpr deque(InputIterator first, InputIterator last, const Allocator& = Allocator()); template<container-compatible-range<T> R> constexpr deque(from_range_t, R&& rg, const Allocator& = Allocator()); constexpr deque(const deque& x); constexpr deque(deque&&); constexpr deque(const deque&, const type_identity_t<Allocator>&); constexpr deque(deque&&, const type_identity_t<Allocator>&); constexpr deque(initializer_list<T>, const Allocator& = Allocator()); constexpr ~deque(); constexpr deque& operator=(const deque& x); constexpr deque& operator=(deque&& x) noexcept(allocator_traits<Allocator>::is_always_equal::value); constexpr deque& operator=(initializer_list<T>); template<class InputIterator> constexpr void assign(InputIterator first, InputIterator last); template<container-compatible-range<T> R> constexpr void assign_range(R&& rg); constexpr void assign(size_type n, const T& t); constexpr void assign(initializer_list<T>); constexpr allocator_type get_allocator() const noexcept; // iterators constexpr iterator begin() noexcept; constexpr const_iterator begin() const noexcept; constexpr iterator end() noexcept; constexpr const_iterator end() const noexcept; constexpr reverse_iterator rbegin() noexcept; constexpr const_reverse_iterator rbegin() const noexcept; constexpr reverse_iterator rend() noexcept; constexpr const_reverse_iterator rend() const noexcept; constexpr const_iterator cbegin() const noexcept; constexpr const_iterator cend() const noexcept; constexpr const_reverse_iterator crbegin() const noexcept; constexpr const_reverse_iterator crend() const noexcept; // [deque.capacity], capacity constexpr bool empty() const noexcept; constexpr size_type size() const noexcept; constexpr size_type max_size() const noexcept; constexpr void resize(size_type sz); constexpr void resize(size_type sz, const T& c); constexpr void shrink_to_fit(); // element access constexpr reference operator[](size_type n); constexpr const_reference operator[](size_type n) const; constexpr reference at(size_type n); constexpr const_reference at(size_type n) const; constexpr reference front(); constexpr const_reference front() const; constexpr reference back(); constexpr const_reference back() const; // [deque.modifiers], modifiers template<class... Args> constexpr reference emplace_front(Args&&... args); template<class... Args> constexpr reference emplace_back(Args&&... args); template<class... Args> constexpr iterator emplace(const_iterator position, Args&&... args); constexpr void push_front(const T& x); constexpr void push_front(T&& x); template<container-compatible-range<T> R> constexpr void prepend_range(R&& rg); constexpr void push_back(const T& x); constexpr void push_back(T&& x); template<container-compatible-range<T> R> constexpr void append_range(R&& rg); constexpr iterator insert(const_iterator position, const T& x); constexpr iterator insert(const_iterator position, T&& x); constexpr iterator insert(const_iterator position, size_type n, const T& x); template<class InputIterator> constexpr iterator insert(const_iterator position, InputIterator first, InputIterator last); template<container-compatible-range<T> R> constexpr iterator insert_range(const_iterator position, R&& rg); constexpr iterator insert(const_iterator position, initializer_list<T>); constexpr void pop_front(); constexpr void pop_back(); constexpr iterator erase(const_iterator position); constexpr iterator erase(const_iterator first, const_iterator last); constexpr void swap(deque&) noexcept(allocator_traits<Allocator>::is_always_equal::value); constexpr void clear() noexcept; }; template<class InputIterator, class Allocator = allocator<iter-value-type<InputIterator>>> deque(InputIterator, InputIterator, Allocator = Allocator()) -> deque<iter-value-type<InputIterator>, Allocator>; template<ranges::input_range R, class Allocator = allocator<ranges::range_value_t<R>>> deque(from_range_t, R&&, Allocator = Allocator()) -> deque<ranges::range_value_t<R>, Allocator>; }

23.3.5.2 Constructors, copy, and assignment [deque.cons]

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constexpr explicit deque(const Allocator&);
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Effects: Constructs an empty deque, using the specified allocator.
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Complexity: Constant.
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constexpr explicit deque(size_type n, const Allocator& = Allocator());
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Preconditions: T is Cpp17DefaultInsertable into deque.
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Effects: Constructs a deque with n default-inserted elements using the specified allocator.
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Complexity: Linear in n.
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constexpr deque(size_type n, const T& value, const Allocator& = Allocator());
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Preconditions: T is Cpp17CopyInsertable into deque.
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Effects: Constructs a deque with n copies of value, using the specified allocator.
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Complexity: Linear in n.
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template<class InputIterator> constexpr deque(InputIterator first, InputIterator last, const Allocator& = Allocator());
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Effects: Constructs a deque equal to the range [first, last), using the specified allocator.
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Complexity: Linear in distance(first, last).
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template<container-compatible-range<T> R> constexpr deque(from_range_t, R&& rg, const Allocator& = Allocator());
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Effects: Constructs a deque with the elements of the range rg, using the specified allocator.
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Complexity: Linear in ranges​::​distance(rg).

23.3.5.3 Capacity [deque.capacity]

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constexpr void resize(size_type sz);
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Preconditions: T is Cpp17MoveInsertable and Cpp17DefaultInsertable into deque.
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Effects: If sz < size(), erases the last size() - sz elements from the sequence.
Otherwise, appends sz - size() default-inserted elements to the sequence.
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constexpr void resize(size_type sz, const T& c);
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Preconditions: T is Cpp17CopyInsertable into deque.
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Effects: If sz < size(), erases the last size() - sz elements from the sequence.
Otherwise, appends sz - size() copies of c to the sequence.
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constexpr void shrink_to_fit();
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Preconditions: T is Cpp17MoveInsertable into deque.
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Effects: shrink_to_fit is a non-binding request to reduce memory use but does not change the size of the sequence.
[Note 1: 
The request is non-binding to allow latitude for implementation-specific optimizations.
— end note]
If the size is equal to the old capacity, or if an exception is thrown other than by the move constructor of a non-Cpp17CopyInsertable T, then there are no effects.
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Complexity: If the size is not equal to the old capacity, linear in the size of the sequence; otherwise constant.
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Remarks: If the size is not equal to the old capacity, then invalidates all the references, pointers, and iterators referring to the elements in the sequence, as well as the past-the-end iterator.

23.3.5.4 Modifiers [deque.modifiers]

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constexpr iterator insert(const_iterator position, const T& x); constexpr iterator insert(const_iterator position, T&& x); constexpr iterator insert(const_iterator position, size_type n, const T& x); template<class InputIterator> constexpr iterator insert(const_iterator position, InputIterator first, InputIterator last); template<container-compatible-range<T> R> constexpr iterator insert_range(const_iterator position, R&& rg); constexpr iterator insert(const_iterator position, initializer_list<T>); template<class... Args> constexpr reference emplace_front(Args&&... args); template<class... Args> constexpr reference emplace_back(Args&&... args); template<class... Args> constexpr iterator emplace(const_iterator position, Args&&... args); constexpr void push_front(const T& x); constexpr void push_front(T&& x); template<container-compatible-range<T> R> constexpr void prepend_range(R&& rg); constexpr void push_back(const T& x); constexpr void push_back(T&& x); template<container-compatible-range<T> R> constexpr void append_range(R&& rg);
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Effects: An insertion in the middle of the deque invalidates all the iterators and references to elements of the deque.
An insertion at either end of the deque invalidates all the iterators to the deque, but has no effect on the validity of references to elements of the deque.
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Complexity: The complexity is linear in the number of elements inserted plus the lesser of the distances to the beginning and end of the deque.
Inserting a single element at either the beginning or end of a deque always takes constant time and causes a single call to a constructor of T.
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Remarks: If an exception is thrown other than by the copy constructor, move constructor, assignment operator, or move assignment operator of T, there are no effects.
If an exception is thrown while inserting a single element at either end, there are no effects.
Otherwise, if an exception is thrown by the move constructor of a non-Cpp17CopyInsertable T, the effects are unspecified.
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constexpr iterator erase(const_iterator position); constexpr iterator erase(const_iterator first, const_iterator last); constexpr void pop_front(); constexpr void pop_back();
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Effects: An erase operation that erases the last element of a deque invalidates only the past-the-end iterator and all iterators and references to the erased elements.
An erase operation that erases the first element of a deque but not the last element invalidates only iterators and references to the erased elements.
An erase operation that erases neither the first element nor the last element of a deque invalidates the past-the-end iterator and all iterators and references to all the elements of the deque.
[Note 1: 
pop_front and pop_back are erase operations.
— end note]
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Throws: Nothing unless an exception is thrown by the assignment operator of T.
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Complexity: The number of calls to the destructor of T is the same as the number of elements erased, but the number of calls to the assignment operator of T is no more than the lesser of the number of elements before the erased elements and the number of elements after the erased elements.

23.3.5.5 Erasure [deque.erasure]

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template<class T, class Allocator, class U = T> constexpr typename deque<T, Allocator>::size_type erase(deque<T, Allocator>& c, const U& value);
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Effects: Equivalent to: auto it = remove(c.begin(), c.end(), value); auto r = distance(it, c.end()); c.erase(it, c.end()); return r;
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template<class T, class Allocator, class Predicate> constexpr typename deque<T, Allocator>::size_type erase_if(deque<T, Allocator>& c, Predicate pred);
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Effects: Equivalent to: auto it = remove_if(c.begin(), c.end(), pred); auto r = distance(it, c.end()); c.erase(it, c.end()); return r;

23.3.6 Header <forward_list> synopsis [forward.list.syn]

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#include <compare> // see [compare.syn] #include <initializer_list> // see [initializer.list.syn] namespace std { // [forward.list], class template forward_list template<class T, class Allocator = allocator<T>> class forward_list; template<class T, class Allocator> constexpr bool operator==(const forward_list<T, Allocator>& x, const forward_list<T, Allocator>& y); template<class T, class Allocator> constexpr synth-three-way-result<T> operator<=>(const forward_list<T, Allocator>& x, const forward_list<T, Allocator>& y); template<class T, class Allocator> constexpr void swap(forward_list<T, Allocator>& x, forward_list<T, Allocator>& y) noexcept(noexcept(x.swap(y))); // [forward.list.erasure], erasure template<class T, class Allocator, class U = T> constexpr typename forward_list<T, Allocator>::size_type erase(forward_list<T, Allocator>& c, const U& value); template<class T, class Allocator, class Predicate> constexpr typename forward_list<T, Allocator>::size_type erase_if(forward_list<T, Allocator>& c, Predicate pred); namespace pmr { template<class T> using forward_list = std::forward_list<T, polymorphic_allocator<T>>; } }

23.3.7 Class template forward_list [forward.list]

23.3.7.1 Overview [forward.list.overview]

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A forward_list is a container that supports forward iterators and allows constant time insert and erase operations anywhere within the sequence, with storage management handled automatically.
Fast random access to list elements is not supported.
[Note 1: 
It is intended that forward_list have zero space or time overhead relative to a hand-written C-style singly linked list.
Features that would conflict with that goal have been omitted.
— end note]
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A forward_list meets all of the requirements of a container ([container.reqmts]), except that the size() member function is not provided and operator== has linear complexity.
A forward_list also meets all of the requirements for an allocator-aware container ([container.alloc.reqmts]).
In addition, a forward_list provides the assign member functions and several of the optional sequence container requirements ([sequence.reqmts]).
Descriptions are provided here only for operations on forward_list that are not described in that table or for operations where there is additional semantic information.
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[Note 2: 
Modifying any list requires access to the element preceding the first element of interest, but in a forward_list there is no constant-time way to access a preceding element.
For this reason, erase_after and splice_after take fully-open ranges, not semi-open ranges.
— end note]
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The types iterator and const_iterator meet the constexpr iterator requirements ([iterator.requirements.general]).
namespace std { template<class T, class Allocator = allocator<T>> class forward_list { public: // types using value_type = T; using allocator_type = Allocator; using pointer = typename allocator_traits<Allocator>::pointer; using const_pointer = typename allocator_traits<Allocator>::const_pointer; using reference = value_type&; using const_reference = const value_type&; using size_type = implementation-defined; // see [container.requirements] using difference_type = implementation-defined; // see [container.requirements] using iterator = implementation-defined; // see [container.requirements] using const_iterator = implementation-defined; // see [container.requirements] // [forward.list.cons], construct/copy/destroy constexpr forward_list() : forward_list(Allocator()) { } constexpr explicit forward_list(const Allocator&); constexpr explicit forward_list(size_type n, const Allocator& = Allocator()); constexpr forward_list(size_type n, const T& value, const Allocator& = Allocator()); template<class InputIterator> constexpr forward_list(InputIterator first, InputIterator last, const Allocator& = Allocator()); template<container-compatible-range<T> R> constexpr forward_list(from_range_t, R&& rg, const Allocator& = Allocator()); constexpr forward_list(const forward_list& x); constexpr forward_list(forward_list&& x); constexpr forward_list(const forward_list& x, const type_identity_t<Allocator>&); constexpr forward_list(forward_list&& x, const type_identity_t<Allocator>&); constexpr forward_list(initializer_list<T>, const Allocator& = Allocator()); constexpr ~forward_list(); constexpr forward_list& operator=(const forward_list& x); constexpr forward_list& operator=(forward_list&& x) noexcept(allocator_traits<Allocator>::is_always_equal::value); constexpr forward_list& operator=(initializer_list<T>); template<class InputIterator> constexpr void assign(InputIterator first, InputIterator last); template<container-compatible-range<T> R> constexpr void assign_range(R&& rg); constexpr void assign(size_type n, const T& t); constexpr void assign(initializer_list<T>); constexpr allocator_type get_allocator() const noexcept; // [forward.list.iter], iterators constexpr iterator before_begin() noexcept; constexpr const_iterator before_begin() const noexcept; constexpr iterator begin() noexcept; constexpr const_iterator begin() const noexcept; constexpr iterator end() noexcept; constexpr const_iterator end() const noexcept; constexpr const_iterator cbegin() const noexcept; constexpr const_iterator cbefore_begin() const noexcept; constexpr const_iterator cend() const noexcept; // capacity constexpr bool empty() const noexcept; constexpr size_type max_size() const noexcept; // [forward.list.access], element access constexpr reference front(); constexpr const_reference front() const; // [forward.list.modifiers], modifiers template<class... Args> constexpr reference emplace_front(Args&&... args); constexpr void push_front(const T& x); constexpr void push_front(T&& x); template<container-compatible-range<T> R> constexpr void prepend_range(R&& rg); constexpr void pop_front(); template<class... Args> constexpr iterator emplace_after(const_iterator position, Args&&... args); constexpr iterator insert_after(const_iterator position, const T& x); constexpr iterator insert_after(const_iterator position, T&& x); constexpr iterator insert_after(const_iterator position, size_type n, const T& x); template<class InputIterator> constexpr iterator insert_after(const_iterator position, InputIterator first, InputIterator last); constexpr iterator insert_after(const_iterator position, initializer_list<T> il); template<container-compatible-range<T> R> constexpr iterator insert_range_after(const_iterator position, R&& rg); constexpr iterator erase_after(const_iterator position); constexpr iterator erase_after(const_iterator position, const_iterator last); constexpr void swap(forward_list&) noexcept(allocator_traits<Allocator>::is_always_equal::value); constexpr void resize(size_type sz); constexpr void resize(size_type sz, const value_type& c); constexpr void clear() noexcept; // [forward.list.ops], forward_list operations constexpr void splice_after(const_iterator position, forward_list& x); constexpr void splice_after(const_iterator position, forward_list&& x); constexpr void splice_after(const_iterator position, forward_list& x, const_iterator i); constexpr void splice_after(const_iterator position, forward_list&& x, const_iterator i); constexpr void splice_after(const_iterator position, forward_list& x, const_iterator first, const_iterator last); constexpr void splice_after(const_iterator position, forward_list&& x, const_iterator first, const_iterator last); constexpr size_type remove(const T& value); template<class Predicate> constexpr size_type remove_if(Predicate pred); size_type unique(); template<class BinaryPredicate> constexpr size_type unique(BinaryPredicate binary_pred); constexpr void merge(forward_list& x); constexpr void merge(forward_list&& x); template<class Compare> constexpr void merge(forward_list& x, Compare comp); template<class Compare> constexpr void merge(forward_list&& x, Compare comp); constexpr void sort(); template<class Compare> constexpr void sort(Compare comp); constexpr void reverse() noexcept; }; template<class InputIterator, class Allocator = allocator<iter-value-type<InputIterator>>> forward_list(InputIterator, InputIterator, Allocator = Allocator()) -> forward_list<iter-value-type<InputIterator>, Allocator>; template<ranges::input_range R, class Allocator = allocator<ranges::range_value_t<R>>> forward_list(from_range_t, R&&, Allocator = Allocator()) -> forward_list<ranges::range_value_t<R>, Allocator>; }
5
#
An incomplete type T may be used when instantiating forward_list if the allocator meets the allocator completeness requirements.
T shall be complete before any member of the resulting specialization of forward_list is referenced.

23.3.7.2 Constructors, copy, and assignment [forward.list.cons]

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constexpr explicit forward_list(const Allocator&);
1
#
Effects: Constructs an empty forward_list object using the specified allocator.
2
#
Complexity: Constant.
🔗
constexpr explicit forward_list(size_type n, const Allocator& = Allocator());
3
#
Preconditions: T is Cpp17DefaultInsertable into forward_list.
4
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Effects: Constructs a forward_list object with n default-inserted elements using the specified allocator.
5
#
Complexity: Linear in n.
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constexpr forward_list(size_type n, const T& value, const Allocator& = Allocator());
6
#
Preconditions: T is Cpp17CopyInsertable into forward_list.
7
#
Effects: Constructs a forward_list object with n copies of value using the specified allocator.
8
#
Complexity: Linear in n.
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template<class InputIterator> constexpr forward_list(InputIterator first, InputIterator last, const Allocator& = Allocator());
9
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Effects: Constructs a forward_list object equal to the range [first, last).
10
#
Complexity: Linear in distance(first, last).
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template<container-compatible-range<T> R> constexpr forward_list(from_range_t, R&& rg, const Allocator& = Allocator());
11
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Effects: Constructs a forward_list object with the elements of the range rg.
12
#
Complexity: Linear in ranges​::​distance(rg).

23.3.7.3 Iterators [forward.list.iter]

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constexpr iterator before_begin() noexcept; constexpr const_iterator before_begin() const noexcept; constexpr const_iterator cbefore_begin() const noexcept;
1
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Effects: cbefore_begin() is equivalent to const_cast<forward_list const&>(*this).before_begin().
2
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Returns: A non-dereferenceable iterator that, when incremented, is equal to the iterator returned by begin().
3
#
Remarks: before_begin() == end() shall equal false.

23.3.7.4 Element access [forward.list.access]

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constexpr reference front(); constexpr const_reference front() const;
1
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Returns: *begin()

23.3.7.5 Modifiers [forward.list.modifiers]

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The member functions in this subclause do not affect the validity of iterators and references when inserting elements, and when erasing elements invalidate iterators and references to the erased elements only.
If an exception is thrown by any of these member functions there is no effect on the container.
Inserting n elements into a forward_list is linear in n, and the number of calls to the copy or move constructor of T is exactly equal to n.
Erasing n elements from a forward_list is linear in n and the number of calls to the destructor of type T is exactly equal to n.
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template<class... Args> constexpr reference emplace_front(Args&&... args);
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Effects: Inserts an object of type value_type constructed with value_type(std​::​forward<Args>(​args)...) at the beginning of the list.
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constexpr void push_front(const T& x); constexpr void push_front(T&& x);
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Effects: Inserts a copy of x at the beginning of the list.
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template<container-compatible-range<T> R> constexpr void prepend_range(R&& rg);
4
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Effects: Inserts a copy of each element of rg at the beginning of the list.
[Note 1: 
The order of elements is not reversed.
— end note]
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constexpr void pop_front();
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Effects: As if by erase_after(before_begin()).
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constexpr iterator insert_after(const_iterator position, const T& x);
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Preconditions: T is Cpp17CopyInsertable into forward_list.
position is before_begin() or is a dereferenceable iterator in the range [begin(), end()).
7
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Effects: Inserts a copy of x after position.
8
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Returns: An iterator pointing to the copy of x.
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constexpr iterator insert_after(const_iterator position, T&& x);
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Preconditions: T is Cpp17MoveInsertable into forward_list.
position is before_begin() or is a dereferenceable iterator in the range [begin(), end()).
10
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Effects: Inserts a copy of x after position.
11
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Returns: An iterator pointing to the copy of x.
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constexpr iterator insert_after(const_iterator position, size_type n, const T& x);
12
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Preconditions: T is Cpp17CopyInsertable into forward_list.
position is before_begin() or is a dereferenceable iterator in the range [begin(), end()).
13
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Effects: Inserts n copies of x after position.
14
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Returns: An iterator pointing to the last inserted copy of x, or position if n == 0 is true.
🔗
template<class InputIterator> constexpr iterator insert_after(const_iterator position, InputIterator first, InputIterator last);
15
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Preconditions: T is Cpp17EmplaceConstructible into forward_list from *first.
position is before_begin() or is a dereferenceable iterator in the range [begin(), end()).
Neither first nor last are iterators in *this.
16
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Effects: Inserts copies of elements in [first, last) after position.
17
#
Returns: An iterator pointing to the last inserted element, or position if first == last is true.
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template<container-compatible-range<T> R> constexpr iterator insert_range_after(const_iterator position, R&& rg);
18
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Preconditions: T is Cpp17EmplaceConstructible into forward_list from *ranges​::​begin(rg).
position is before_begin() or is a dereferenceable iterator in the range [begin(), end()).
rg and *this do not overlap.
19
#
Effects: Inserts copies of elements in the range rg after position.
20
#
Returns: An iterator pointing to the last inserted element, or position if rg is empty.
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constexpr iterator insert_after(const_iterator position, initializer_list<T> il);
21
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Effects: Equivalent to: return insert_after(position, il.begin(), il.end());
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template<class... Args> constexpr iterator emplace_after(const_iterator position, Args&&... args);
22
#
Preconditions: T is Cpp17EmplaceConstructible into forward_list from std​::​forward<Args>(args)....
position is before_begin() or is a dereferenceable iterator in the range [begin(), end()).
23
#
Effects: Inserts an object of type value_type direct-non-list-initialized with std​::​forward<Args>(args)... after position.
24
#
Returns: An iterator pointing to the new object.
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constexpr iterator erase_after(const_iterator position);
25
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Preconditions: The iterator following position is dereferenceable.
26
#
Effects: Erases the element pointed to by the iterator following position.
27
#
Returns: An iterator pointing to the element following the one that was erased, or end() if no such element exists.
28
#
Throws: Nothing.
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constexpr iterator erase_after(const_iterator position, const_iterator last);
29
#
Preconditions: All iterators in the range (position, last) are dereferenceable.
30
#
Effects: Erases the elements in the range (position, last).
31
#
Returns: last.
32
#
Throws: Nothing.
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constexpr void resize(size_type sz);
33
#
Preconditions: T is Cpp17DefaultInsertable into forward_list.
34
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Effects: If sz < distance(begin(), end()), erases the last distance(begin(), end()) - sz elements from the list.
Otherwise, inserts sz - distance(begin(), end()) default-inserted elements at the end of the list.
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constexpr void resize(size_type sz, const value_type& c);
35
#
Preconditions: T is Cpp17CopyInsertable into forward_list.
36
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Effects: If sz < distance(begin(), end()), erases the last distance(begin(), end()) - sz elements from the list.
Otherwise, inserts sz - distance(begin(), end()) copies of c at the end of the list.
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constexpr void clear() noexcept;
37
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Effects: Erases all elements in the range [begin(), end()).
38
#
Remarks: Does not invalidate past-the-end iterators.

23.3.7.6 Operations [forward.list.ops]

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In this subclause, arguments for a template parameter named Predicate or BinaryPredicate shall meet the corresponding requirements in [algorithms.requirements].
The semantics of i + n, where i is an iterator into the list and n is an integer, are the same as those of next(i, n).
The expression i - n, where i is an iterator into the list and n is an integer, means an iterator j such that j + n == i is true.
For merge and sort, the definitions and requirements in [alg.sorting] apply.
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constexpr void splice_after(const_iterator position, forward_list& x); constexpr void splice_after(const_iterator position, forward_list&& x);
2
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Preconditions: position is before_begin() or is a dereferenceable iterator in the range [begin(), end()).
get_allocator() == x.get_allocator() is true.
addressof(x) != this is true.
3
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Effects: Inserts the contents of x after position, and x becomes empty.
Pointers and references to the moved elements of x now refer to those same elements but as members of *this.
Iterators referring to the moved elements will continue to refer to their elements, but they now behave as iterators into *this, not into x.
4
#
Throws: Nothing.
5
#
Complexity:
🔗
constexpr void splice_after(const_iterator position, forward_list& x, const_iterator i); constexpr void splice_after(const_iterator position, forward_list&& x, const_iterator i);
6
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Preconditions: position is before_begin() or is a dereferenceable iterator in the range [begin(), end()).
The iterator following i is a dereferenceable iterator in x.
get_allocator() == x.get_allocator() is true.
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Effects: Inserts the element following i into *this, following position, and removes it from x.
The result is unchanged if position == i or position == ++i.
Pointers and references to *++i continue to refer to the same element but as a member of *this.
Iterators to *++i continue to refer to the same element, but now behave as iterators into *this, not into x.
8
#
Throws: Nothing.
9
#
Complexity:
🔗
constexpr void splice_after(const_iterator position, forward_list& x, const_iterator first, const_iterator last); constexpr void splice_after(const_iterator position, forward_list&& x, const_iterator first, const_iterator last);
10
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Preconditions: position is before_begin() or is a dereferenceable iterator in the range [begin(), end()).
(first, last) is a valid range in x, and all iterators in the range (first, last) are dereferenceable.
position is not an iterator in the range (first, last).
get_allocator() == x.get_allocator() is true.
11
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Effects: Inserts elements in the range (first, last) after position and removes the elements from x.
Pointers and references to the moved elements of x now refer to those same elements but as members of *this.
Iterators referring to the moved elements will continue to refer to their elements, but they now behave as iterators into *this, not into x.
12
#
Complexity:
🔗
constexpr size_type remove(const T& value); template<class Predicate> constexpr size_type remove_if(Predicate pred);
13
#
Effects: Erases all the elements in the list referred to by a list iterator i for which the following conditions hold: *i == value (for remove()), pred(*i) is true (for remove_if()).
Invalidates only the iterators and references to the erased elements.
14
#
Returns: The number of elements erased.
15
#
Throws: Nothing unless an exception is thrown by the equality comparison or the predicate.
16
#
Complexity: Exactly distance(begin(), end()) applications of the corresponding predicate.
17
#
Remarks: Stable.
🔗
constexpr size_type unique(); template<class BinaryPredicate> constexpr size_type unique(BinaryPredicate binary_pred);
18
#
Let binary_pred be equal_to<>{} for the first overload.
19
#
Preconditions: binary_pred is an equivalence relation.
20
#
Effects: Erases all but the first element from every consecutive group of equivalent elements.
That is, for a nonempty list, erases all elements referred to by the iterator i in the range [begin() + 1, end()) for which binary_pred(*i, *(i - 1)) is true.
Invalidates only the iterators and references to the erased elements.
21
#
Returns: The number of elements erased.
22
#
Throws: Nothing unless an exception is thrown by the predicate.
23
#
Complexity: If empty() is false, exactly distance(begin(), end()) - 1 applications of the corresponding predicate, otherwise no applications of the predicate.
🔗
constexpr void merge(forward_list& x); constexpr void merge(forward_list&& x); template<class Compare> constexpr void merge(forward_list& x, Compare comp); template<class Compare> constexpr void merge(forward_list&& x, Compare comp);
24
#
Let comp be less<> for the first two overloads.
25
#
Preconditions: *this and x are both sorted with respect to the comparator comp, and get_allocator() == x.get_allocator() is true.
26
#
Effects: If addressof(x) == this, there are no effects.
Otherwise, merges the two sorted ranges [begin(), end()) and [x.begin(), x.end()).
The result is a range that is sorted with respect to the comparator comp.
Pointers and references to the moved elements of x now refer to those same elements but as members of *this.
Iterators referring to the moved elements will continue to refer to their elements, but they now behave as iterators into *this, not into x.
27
#
Complexity: At most distance(begin(), end()) + distance(x.begin(), x.end()) - 1 comparisons if addressof(x) != this; otherwise, no comparisons are performed.
28
#
Remarks: Stable ([algorithm.stable]).
If addressof(x) != this, x is empty after the merge.
No elements are copied by this operation.
If an exception is thrown other than by a comparison, there are no effects.
🔗
constexpr void sort(); template<class Compare> constexpr void sort(Compare comp);
29
#
Effects: Sorts the list according to the operator< or the comp function object.
If an exception is thrown, the order of the elements in *this is unspecified.
Does not affect the validity of iterators and references.
30
#
Complexity: Approximately comparisons, where N is distance(begin(), end()).
31
#
Remarks: Stable.
🔗
constexpr void reverse() noexcept;
32
#
Effects: Reverses the order of the elements in the list.
Does not affect the validity of iterators and references.
33
#
Complexity: Linear time.

23.3.7.7 Erasure [forward.list.erasure]

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template<class T, class Allocator, class U = T> constexpr typename forward_list<T, Allocator>::size_type erase(forward_list<T, Allocator>& c, const U& value);
1
#
Effects: Equivalent to: return erase_if(c, [&](const auto& elem) -> bool { return elem == value; });
🔗
template<class T, class Allocator, class Predicate> constexpr typename forward_list<T, Allocator>::size_type erase_if(forward_list<T, Allocator>& c, Predicate pred);
2
#
Effects: Equivalent to: return c.remove_if(pred);

23.3.8 Header <hive> synopsis [hive.syn]

🔗
#include <initializer_list> // see [initializer.list.syn] #include <compare> // see [compare.syn] namespace std { struct hive_limits { size_t min; size_t max; constexpr hive_limits(size_t minimum, size_t maximum) noexcept : min(minimum), max(maximum) {} }; // [hive], class template hive template<class T, class Allocator = allocator<T>> class hive; template<class T, class Allocator> void swap(hive<T, Allocator>& x, hive<T, Allocator>& y) noexcept(noexcept(x.swap(y))); template<class T, class Allocator, class U = T> typename hive<T, Allocator>::size_type erase(hive<T, Allocator>& c, const U& value); template<class T, class Allocator, class Predicate> typename hive<T, Allocator>::size_type erase_if(hive<T, Allocator>& c, Predicate pred); namespace pmr { template<class T> using hive = std::hive<T, polymorphic_allocator<T>>; } }

23.3.9 Class template hive [hive]

23.3.9.1 Overview [hive.overview]

1
#
A hive is a type of sequence container that provides constant-time insertion and erasure operations.
Storage is automatically managed in multiple memory blocks, referred to as element blocks.
Insertion position is determined by the container, and insertion may re-use the memory locations of erased elements.
2
#
Element blocks which contain elements are referred to as active blocks, those which do not are referred to as reserved blocks.
Active blocks which become empty of elements are either deallocated or become reserved blocks.
Reserved blocks become active blocks when they are used to store elements.
A user can create additional reserved blocks by calling reserve.
3
#
Erasures use unspecified techniques of constant time complexity to identify the memory locations of erased elements, which are subsequently skipped during iteration, as opposed to relocating subsequent elements during erasure.
4
#
Active block capacities have an implementation-defined growth factor (which need not be integral), for example a new active block's capacity could be equal to the summed capacities of the pre-existing active blocks.
5
#
Limits can be placed on both the minimum and maximum element capacities of element blocks, both by users and implementations.
  • (5.1)
    The minimum limit shall be no larger than the maximum limit.
  • (5.2)
    When limits are not specified by a user during construction, the implementation's default limits are used.
  • (5.3)
    The default limits of an implementation are not guaranteed to be the same as the minimum and maximum possible capacities for an implementation's element blocks.
    [Note 1: 
    To allow latitude for both implementation-specific and user-directed optimization.
    — end note]
    The latter are defined as hard limits.
    The maximum hard limit shall be no larger than std​::​allocator_traits<Allocator>​::​max_size().
  • (5.4)
    If user-specified limits are not within hard limits, or if the specified minimum limit is greater than the specified maximum limit, the behavior is undefined.
  • (5.5)
    An element block is said to be within the bounds of a pair of minimum/maximum limits when its capacity is greater-or-equal-to the minimum limit and less-than-or-equal-to the maximum limit.
6
#
A hive conforms to the requirements for containers ([container.reqmts]), with the exception of operators == and !=.
A hive also meets the requirements of a reversible container ([container.rev.reqmts]), of an allocator-aware container ([container.alloc.reqmts]), and some of the requirements of a sequence container ([sequence.reqmts]).
Descriptions are provided here only for operations on hive that are not described in that table or for operations where there is additional semantic information.
7
#
The iterators of hive meet the Cpp17BidirectionalIterator requirements but also model three_way_comparable<strong_ordering>.
namespace std { template<class T, class Allocator = allocator<T>> class hive { public: // types using value_type = T; using allocator_type = Allocator; using pointer = typename allocator_traits<Allocator>::pointer; using const_pointer = typename allocator_traits<Allocator>::const_pointer; using reference = value_type&; using const_reference = const value_type&; using size_type = implementation-defined; // see [container.requirements] using difference_type = implementation-defined; // see [container.requirements] using iterator = implementation-defined; // see [container.requirements] using const_iterator = implementation-defined; // see [container.requirements] using reverse_iterator = std::reverse_iterator<iterator>; // see [container.requirements] using const_reverse_iterator = std::reverse_iterator<const_iterator>; // see [container.requirements] // [hive.cons], construct/copy/destroy constexpr hive() noexcept(noexcept(Allocator())) : hive(Allocator()) {} constexpr explicit hive(const Allocator&) noexcept; constexpr explicit hive(hive_limits block_limits) : hive(block_limits, Allocator()) {} constexpr hive(hive_limits block_limits, const Allocator&); explicit hive(size_type n, const Allocator& = Allocator()); hive(size_type n, hive_limits block_limits, const Allocator& = Allocator()); hive(size_type n, const T& value, const Allocator& = Allocator()); hive(size_type n, const T& value, hive_limits block_limits, const Allocator& = Allocator()); template<class InputIterator> hive(InputIterator first, InputIterator last, const Allocator& = Allocator()); template<class InputIterator> hive(InputIterator first, InputIterator last, hive_limits block_limits, const Allocator& = Allocator()); template<container-compatible-range<T> R> hive(from_range_t, R&& rg, const Allocator& = Allocator()); template<container-compatible-range<T> R> hive(from_range_t, R&& rg, hive_limits block_limits, const Allocator& = Allocator()); hive(const hive& x); hive(hive&&) noexcept; hive(const hive& x, const type_identity_t<Allocator>& alloc); hive(hive&&, const type_identity_t<Allocator>& alloc); hive(initializer_list<T> il, const Allocator& = Allocator()); hive(initializer_list<T> il, hive_limits block_limits, const Allocator& = Allocator()); ~hive(); hive& operator=(const hive& x); hive& operator=(hive&& x) noexcept(see below); hive& operator=(initializer_list<T>); template<class InputIterator> void assign(InputIterator first, InputIterator last); template<container-compatible-range<T> R> void assign_range(R&& rg); void assign(size_type n, const T& t); void assign(initializer_list<T>); allocator_type get_allocator() const noexcept; // iterators iterator begin() noexcept; const_iterator begin() const noexcept; iterator end() noexcept; const_iterator end() const noexcept; reverse_iterator rbegin() noexcept; const_reverse_iterator rbegin() const noexcept; reverse_iterator rend() noexcept; const_reverse_iterator rend() const noexcept; const_iterator cbegin() const noexcept; const_iterator cend() const noexcept; const_reverse_iterator crbegin() const noexcept; const_reverse_iterator crend() const noexcept; // [hive.capacity], capacity bool empty() const noexcept; size_type size() const noexcept; size_type max_size() const noexcept; size_type capacity() const noexcept; void reserve(size_type n); void shrink_to_fit(); void trim_capacity() noexcept; void trim_capacity(size_type n) noexcept; constexpr hive_limits block_capacity_limits() const noexcept; static constexpr hive_limits block_capacity_default_limits() noexcept; static constexpr hive_limits block_capacity_hard_limits() noexcept; void reshape(hive_limits block_limits); // [hive.modifiers], modifiers template<class... Args> iterator emplace(Args&&... args); template<class... Args> iterator emplace_hint(const_iterator hint, Args&&... args); iterator insert(const T& x); iterator insert(T&& x); iterator insert(const_iterator hint, const T& x); iterator insert(const_iterator hint, T&& x); void insert(initializer_list<T> il); template<container-compatible-range<T> R> void insert_range(R&& rg); template<class InputIterator> void insert(InputIterator first, InputIterator last); void insert(size_type n, const T& x); iterator erase(const_iterator position); iterator erase(const_iterator first, const_iterator last); void swap(hive&) noexcept(see below); void clear() noexcept; // [hive.operations], hive operations void splice(hive& x); void splice(hive&& x); template<class BinaryPredicate = equal_to<T>> size_type unique(BinaryPredicate binary_pred = BinaryPredicate()); template<class Compare = less<T>> void sort(Compare comp = Compare()); iterator get_iterator(const_pointer p) noexcept; const_iterator get_iterator(const_pointer p) const noexcept; private: hive_limits current-limits = implementation-defined; // exposition only }; template<class InputIterator, class Allocator = allocator<iter-value-type<InputIterator>>> hive(InputIterator, InputIterator, Allocator = Allocator()) -> hive<iter-value-type<InputIterator>, Allocator>; template<class InputIterator, class Allocator = allocator<iter-value-type<InputIterator>>> hive(InputIterator, InputIterator, hive_limits, Allocator = Allocator()) -> hive<iter-value-type<InputIterator>, Allocator>; template<ranges::input_range R, class Allocator = allocator<ranges::range_value_t<R>>> hive(from_range_t, R&&, Allocator = Allocator()) -> hive<ranges::range_value_t<R>, Allocator>; template<ranges::input_range R, class Allocator = allocator<ranges::range_value_t<R>>> hive(from_range_t, R&&, hive_limits, Allocator = Allocator()) -> hive<ranges::range_value_t<R>, Allocator>; }

23.3.9.2 Constructors, copy, and assignment [hive.cons]

🔗
constexpr explicit hive(const Allocator&) noexcept;
1
#
Effects: Constructs an empty hive, using the specified allocator.
2
#
Complexity: Constant.
🔗
constexpr hive(hive_limits block_limits, const Allocator&);
3
#
Effects: Constructs an empty hive, using the specified allocator.
Initializes current-limits with block_limits.
4
#
Complexity: Constant.
🔗
explicit hive(size_type n, const Allocator& = Allocator()); hive(size_type n, hive_limits block_limits, const Allocator& = Allocator());
5
#
Preconditions: T is Cpp17DefaultInsertable into hive.
6
#
Effects: Constructs a hive with n default-inserted elements, using the specified allocator.
If the second overload is called, also initializes current-limits with block_limits.
7
#
Complexity: Linear in n.
🔗
hive(size_type n, const T& value, const Allocator& = Allocator()); hive(size_type n, const T& value, hive_limits block_limits, const Allocator& = Allocator());
8
#
Preconditions: T is Cpp17CopyInsertable into hive.
9
#
Effects: Constructs a hive with n copies of value, using the specified allocator.
If the second overload is called, also initializes current-limits with block_limits.
10
#
Complexity: Linear in n.
🔗
template<class InputIterator> hive(InputIterator first, InputIterator last, const Allocator& = Allocator()); template<class InputIterator> hive(InputIterator first, InputIterator last, hive_limits block_limits, const Allocator& = Allocator());
11
#
Effects: Constructs a hive equal to the range [first, last), using the specified allocator.
If the second overload is called, also initializes current-limits with block_limits.
12
#
Complexity: Linear in distance(first, last).
🔗
template<container-compatible-range<T> R> hive(from_range_t, R&& rg, const Allocator& = Allocator()); template<container-compatible-range<T> R> hive(from_range_t, R&& rg, hive_limits block_limits, const Allocator& = Allocator());
13
#
Effects: Constructs a hive object with the elements of the range rg, using the specified allocator.
If the second overload is called, also initializes current-limits with block_limits.
14
#
Complexity: Linear in ranges​::​distance(rg).
🔗
hive(const hive& x); hive(const hive& x, const type_identity_t<Allocator>& alloc);
15
#
Preconditions: T is Cpp17CopyInsertable into hive.
16
#
Effects: Constructs a hive object with the elements of x.
If the second overload is called, uses alloc.
Initializes current-limits with x.current-limits.
17
#
Complexity: Linear in x.size().
🔗
hive(hive&& x); hive(hive&& x, const type_identity_t<Allocator>& alloc);
18
#
Preconditions: For the second overload, when allocator_traits<alloc>​::​is_always_equal​::​value is false, T meets the Cpp17MoveInsertable requirements.
19
#
Effects: When the first overload is called, or the second overload is called and alloc == x.get_allocator() is true, current-limits is set to x.current-limits and each element block is moved from x into *this.
Pointers and references to the elements of x now refer to those same elements but as members of *this.
Iterators referring to the elements of x will continue to refer to their elements, but they now behave as iterators into *this.
If the second overload is called and alloc == x.get_allocator() is false, each element in x is moved into *this.
References, pointers and iterators referring to the elements of x, as well as the past-the-end iterator of x, are invalidated.
20
#
Postconditions: x.empty() is true.
21
#
Complexity: If the second overload is called and alloc == x.get_allocator() is false, linear in x.size().
Otherwise constant.
🔗
hive(initializer_list<T> il, const Allocator& = Allocator()); hive(initializer_list<T> il, hive_limits block_limits, const Allocator& = Allocator());
22
#
Preconditions: T is Cpp17CopyInsertable into hive.
23
#
Effects: Constructs a hive object with the elements of il, using the specified allocator.
If the second overload is called, also initializes current-limits with block_limits.
24
#
Complexity: Linear in il.size().
🔗
hive& operator=(const hive& x);
25
#
Preconditions: T is Cpp17CopyInsertable into hive and Cpp17CopyAssignable.
26
#
Effects: All elements in *this are either copy-assigned to, or destroyed.
All elements in x are copied into *this.
[Note 1: 
current-limits is unchanged.
— end note]
27
#
Complexity: Linear in size() + x.size().
🔗
hive& operator=(hive&& x) noexcept(allocator_traits<Allocator>::propagate_on_container_move_assignment::value || allocator_traits<Allocator>::is_always_equal::value);
28
#
Preconditions: When (allocator_traits<Allocator>::propagate_on_container_move_assignment::value || allocator_traits<Allocator>::is_always_equal::value) is false, T is Cpp17MoveInsertable into hive and Cpp17MoveAssignable.
29
#
Effects: Each element in *this is either move-assigned to, or destroyed.
When (allocator_traits<Allocator>::propagate_on_container_move_assignment::value || get_allocator() == x.get_allocator()) is true, current-limits is set to x.current-limits and each element block is moved from x into *this.
Pointers and references to the elements of x now refer to those same elements but as members of *this.
Iterators referring to the elements of x will continue to refer to their elements, but they now behave as iterators into *this, not into x.
When (allocator_traits<Allocator>::propagate_on_container_move_assignment::value || get_allocator() == x.get_allocator()) is false, each element in x is moved into *this.
References, pointers and iterators referring to the elements of x, as well as the past-the-end iterator of x, are invalidated.
30
#
Postconditions: x.empty() is true.
31
#
Complexity: Linear in size().
If (allocator_traits<Allocator>::propagate_on_container_move_assignment::value || get_allocator() == x.get_allocator()) is false, also linear in x.size().

23.3.9.3 Capacity [hive.capacity]

🔗
size_type capacity() const noexcept;
1
#
Returns: The total number of elements that *this can hold without requiring allocation of more element blocks.
2
#
Complexity: Constant.
🔗
void reserve(size_type n);
3
#
Effects: If n <= capacity() is true, there are no effects.
Otherwise increases capacity() by allocating reserved blocks.
4
#
Postconditions: capacity() >= n is true.
5
#
Throws: length_error if n > max_size(), as well as any exceptions thrown by the allocator.
6
#
Complexity: It does not change the size of the sequence and takes at most linear time in the number of reserved blocks allocated.
7
#
Remarks: All references, pointers, and iterators referring to elements in *this, as well as the past-the-end iterator, remain valid.
🔗
void shrink_to_fit();
8
#
Preconditions: T is Cpp17MoveInsertable into hive.
9
#
Effects: shrink_to_fit is a non-binding request to reduce capacity() to be closer to size().
[Note 1: 
The request is non-binding to allow latitude for implementation-specific optimizations.
— end note]
It does not increase capacity(), but may reduce capacity().
It may reallocate elements.
If capacity() is already equal to size(), there are no effects.
If an exception is thrown during allocation of a new element block, capacity() may be reduced and reallocation may occur.
Otherwise if an exception is thrown, the effects are unspecified.
10
#
Complexity: If reallocation happens, linear in the size of the sequence.
11
#
Remarks: If reallocation happens, the order of the elements in *this may change and all references, pointers, and iterators referring to the elements in *this, as well as the past-the-end iterator, are invalidated.
🔗
void trim_capacity() noexcept; void trim_capacity(size_type n) noexcept;
12
#
Effects: For the first overload, all reserved blocks are deallocated, and capacity() is reduced accordingly.
For the second overload, capacity() is reduced to no less than n.
13
#
Complexity: Linear in the number of reserved blocks deallocated.
14
#
Remarks: All references, pointers, and iterators referring to elements in *this, as well as the past-the-end iterator, remain valid.
🔗
constexpr hive_limits block_capacity_limits() const noexcept;
15
#
Returns: current-limits.
16
#
Complexity: Constant.
🔗
static constexpr hive_limits block_capacity_default_limits() noexcept;
17
#
Returns: A hive_limits struct with the min and max members set to the implementation's default limits.
18
#
Complexity: Constant.
🔗
static constexpr hive_limits block_capacity_hard_limits() noexcept;
19
#
Returns: A hive_limits struct with the min and max members set to the implementation's hard limits.
20
#
Complexity: Constant.
🔗
void reshape(hive_limits block_limits);
21
#
Preconditions: T is Cpp17MoveInsertable into hive.
22
#
Effects: For any active blocks not within the bounds of block_limits, the elements within those active blocks are reallocated to new or existing element blocks which are within the bounds.
Any element blocks not within the bounds of block_limits are deallocated.
If an exception is thrown during allocation of a new element block, capacity() may be reduced, reallocation may occur, and current-limits may be assigned a value other than block_limits.
Otherwise block_limits is assigned to current-limits.
If any other exception is thrown the effects are unspecified.
23
#
Postconditions: size() is unchanged.
24
#
Complexity: Linear in the number of element blocks in *this.
If reallocation happens, also linear in the number of elements reallocated.
25
#
Remarks: This operation may change capacity().
If reallocation happens, the order of the elements in *this may change.
Reallocation invalidates all references, pointers, and iterators referring to the elements in *this, as well as the past-the-end iterator.
[Note 2: 
If no reallocation happens, they remain valid.
— end note]

23.3.9.4 Modifiers [hive.modifiers]

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template<class... Args> iterator emplace(Args&&... args); template<class... Args> iterator emplace_hint(const_iterator hint, Args&&... args);
1
#
Preconditions: T is Cpp17EmplaceConstructible into hive from args.
2
#
Effects: Inserts an object of type T constructed with std​::​forward<Args>(args)....
The hint parameter is ignored.
If an exception is thrown, there are no effects.
[Note 1: 
args can directly or indirectly refer to a value in *this.
— end note]
3
#
Returns: An iterator that points to the new element.
4
#
Complexity: Constant.
Exactly one object of type T is constructed.
5
#
Remarks: Invalidates the past-the-end iterator.
🔗
iterator insert(const T& x); iterator insert(const_iterator hint, const T& x); iterator insert(T&& x); iterator insert(const_iterator hint, T&& x);
6
#
Effects: Equivalent to: return emplace(std​::​forward<decltype(x)>(x));
[Note 2: 
The hint parameter is ignored.
— end note]
🔗
void insert(initializer_list<T> rg); template<container-compatible-range<T> R> void insert_range(R&& rg);
7
#
Preconditions: T is Cpp17EmplaceInsertable into hive from *ranges​::​begin(rg).
rg and *this do not overlap.
8
#
Effects: Inserts copies of elements in rg.
Each iterator in the range rg is dereferenced exactly once.
9
#
Complexity: Linear in the number of elements inserted.
Exactly one object of type T is constructed for each element inserted.
10
#
Remarks: If an element is inserted, invalidates the past-the-end iterator.
🔗
void insert(size_type n, const T& x);
11
#
Preconditions: T is Cpp17CopyInsertable into hive.
12
#
Effects: Inserts n copies of x.
13
#
Complexity: Linear in n.
Exactly one object of type T is constructed for each element inserted.
14
#
Remarks: If an element is inserted, invalidates the past-the-end iterator.
🔗
template<class InputIterator> void insert(InputIterator first, InputIterator last);
15
#
Effects: Equivalent to insert_range(ranges​::​subrange(first, last)).
🔗
iterator erase(const_iterator position); iterator erase(const_iterator first, const_iterator last);
16
#
Complexity: Linear in the number of elements erased.
Additionally, if any active blocks become empty of elements as a result of the function call, at worst linear in the number of element blocks.
17
#
Remarks: Invalidates references, pointers and iterators referring to the erased elements.
An erase operation that erases the last element in *this also invalidates the past-the-end iterator.
🔗
void swap(hive& x) noexcept(allocator_traits<Allocator>::propagate_on_container_swap::value || allocator_traits<Allocator>::is_always_equal::value);
18
#
Effects: Exchanges the contents, capacity(), and current-limits of *this with that of x.
19
#
Complexity: Constant.

23.3.9.5 Operations [hive.operations]

In this subclause, arguments for a template parameter named Predicate or BinaryPredicate shall meet the corresponding requirements in [algorithms.requirements].
The semantics of i + n and i - n, where i is an iterator into the hive and n is an integer, are the same as those of next(i, n) and prev(i, n), respectively.
For sort, the definitions and requirements in [alg.sorting] apply.
🔗
void splice(hive& x); void splice(hive&& x);
1
#
Preconditions: get_allocator() == x.get_allocator() is true.
2
#
Effects: If addressof(x) == this is true, the behavior is erroneous and there are no effects.
Otherwise, inserts the contents of x into *this and x becomes empty.
Pointers and references to the moved elements of x now refer to those same elements but as members of *this.
Iterators referring to the moved elements continue to refer to their elements, but they now behave as iterators into *this, not into x.
3
#
Throws: length_error if any of x's active blocks are not within the bounds of current-limits.
4
#
Complexity: Linear in the sum of all element blocks in x plus all element blocks in *this.
5
#
Remarks: Reserved blocks in x are not transferred into *this.
If addressof(x) == this is false, invalidates the past-the-end iterator for both x and *this.
🔗
template<class BinaryPredicate = equal_to<T>> size_type unique(BinaryPredicate binary_pred = BinaryPredicate());
6
#
Preconditions: binary_pred is an equivalence relation.
7
#
Effects: Erases all but the first element from every consecutive group of equivalent elements.
That is, for a nonempty hive, erases all elements referred to by the iterator i in the range [begin() + 1, end()) for which binary_pred(*i, *(i - 1)) is true.
8
#
Returns: The number of elements erased.
9
#
Throws: Nothing unless an exception is thrown by the predicate.
10
#
Complexity: If empty() is false, exactly size() - 1 applications of the corresponding predicate, otherwise no applications of the predicate.
11
#
Remarks: Invalidates references, pointers, and iterators referring to the erased elements.
If the last element in *this is erased, also invalidates the past-the-end iterator.
🔗
template<class Compare = less<T>> void sort(Compare comp = Compare());
12
#
Preconditions: T is Cpp17MoveInsertable into hive, Cpp17MoveAssignable, and Cpp17Swappable.
13
#
Effects: Sorts *this according to the comp function object.
If an exception is thrown, the order of the elements in *this is unspecified.
14
#
Complexity: comparisons, where N is size().
15
#
Remarks: May allocate.
References, pointers, and iterators referring to elements in *this, as well as the past-the-end iterator, may be invalidated.
[Note 1: 
Not required to be stable[algorithm.stable].
— end note]
🔗
iterator get_iterator(const_pointer p) noexcept; const_iterator get_iterator(const_pointer p) const noexcept;
16
#
Preconditions: p points to an element in *this.
17
#
Returns: An iterator or const_iterator pointing to the same element as p.
18
#
Complexity: Linear in the number of active blocks in *this.

23.3.9.6 Erasure [hive.erasure]

🔗
template<class T, class Allocator, class U> typename hive<T, Allocator>::size_type erase(hive<T, Allocator>& c, const U& value);
1
#
Effects: Equivalent to: return erase_if(c, [&](auto& elem) { return elem == value; });
🔗
template<class T, class Allocator, class Predicate> typename hive<T, Allocator>::size_type erase_if(hive<T, Allocator>& c, Predicate pred);
2
#
Effects: Equivalent to: auto original_size = c.size(); for (auto i = c.begin(), last = c.end(); i != last; ) { if (pred(*i)) { i = c.erase(i); } else { ++i; } } return original_size - c.size();

23.3.10 Header <list> synopsis [list.syn]

🔗
#include <compare> // see [compare.syn] #include <initializer_list> // see [initializer.list.syn] namespace std { // [list], class template list template<class T, class Allocator = allocator<T>> class list; template<class T, class Allocator> constexpr bool operator==(const list<T, Allocator>& x, const list<T, Allocator>& y); template<class T, class Allocator> constexpr synth-three-way-result<T> operator<=>(const list<T, Allocator>& x, const list<T, Allocator>& y); template<class T, class Allocator> constexpr void swap(list<T, Allocator>& x, list<T, Allocator>& y) noexcept(noexcept(x.swap(y))); // [list.erasure], erasure template<class T, class Allocator, class U = T> constexpr typename list<T, Allocator>::size_type erase(list<T, Allocator>& c, const U& value); template<class T, class Allocator, class Predicate> constexpr typename list<T, Allocator>::size_type erase_if(list<T, Allocator>& c, Predicate pred); namespace pmr { template<class T> using list = std::list<T, polymorphic_allocator<T>>; } }

23.3.11 Class template list [list]

23.3.11.1 Overview [list.overview]

1
#
A list is a sequence container that supports bidirectional iterators and allows constant time insert and erase operations anywhere within the sequence, with storage management handled automatically.
Unlike vectors and deques, fast random access to list elements is not supported, but many algorithms only need sequential access anyway.
2
#
A list meets all of the requirements of a container ([container.reqmts]), of a reversible container ([container.rev.reqmts]), of an allocator-aware container ([container.alloc.reqmts]), and of a sequence container, including most of the optional sequence container requirements ([sequence.reqmts]).
The exceptions are the operator[] and at member functions, which are not provided.196
Descriptions are provided here only for operations on list that are not described in one of these tables or for operations where there is additional semantic information.
3
#
The types iterator and const_iterator meet the constexpr iterator requirements[iterator.requirements.general].
namespace std { template<class T, class Allocator = allocator<T>> class list { public: // types using value_type = T; using allocator_type = Allocator; using pointer = typename allocator_traits<Allocator>::pointer; using const_pointer = typename allocator_traits<Allocator>::const_pointer; using reference = value_type&; using const_reference = const value_type&; using size_type = implementation-defined; // see [container.requirements] using difference_type = implementation-defined; // see [container.requirements] using iterator = implementation-defined; // see [container.requirements] using const_iterator = implementation-defined; // see [container.requirements] using reverse_iterator = std::reverse_iterator<iterator>; using const_reverse_iterator = std::reverse_iterator<const_iterator>; // [list.cons], construct/copy/destroy constexpr list() : list(Allocator()) { } constexpr explicit list(const Allocator&); constexpr explicit list(size_type n, const Allocator& = Allocator()); constexpr list(size_type n, const T& value, const Allocator& = Allocator()); template<class InputIterator> constexpr list(InputIterator first, InputIterator last, const Allocator& = Allocator()); template<container-compatible-range<T> R> constexpr list(from_range_t, R&& rg, const Allocator& = Allocator()); constexpr list(const list& x); constexpr list(list&& x); constexpr list(const list&, const type_identity_t<Allocator>&); constexpr list(list&&, const type_identity_t<Allocator>&); constexpr list(initializer_list<T>, const Allocator& = Allocator()); constexpr ~list(); constexpr list& operator=(const list& x); constexpr list& operator=(list&& x) noexcept(allocator_traits<Allocator>::is_always_equal::value); constexpr list& operator=(initializer_list<T>); template<class InputIterator> constexpr void assign(InputIterator first, InputIterator last); template<container-compatible-range<T> R> constexpr void assign_range(R&& rg); constexpr void assign(size_type n, const T& t); constexpr void assign(initializer_list<T>); constexpr allocator_type get_allocator() const noexcept; // iterators constexpr iterator begin() noexcept; constexpr const_iterator begin() const noexcept; constexpr iterator end() noexcept; constexpr const_iterator end() const noexcept; constexpr reverse_iterator rbegin() noexcept; constexpr const_reverse_iterator rbegin() const noexcept; constexpr reverse_iterator rend() noexcept; constexpr const_reverse_iterator rend() const noexcept; constexpr const_iterator cbegin() const noexcept; constexpr const_iterator cend() const noexcept; constexpr const_reverse_iterator crbegin() const noexcept; constexpr const_reverse_iterator crend() const noexcept; // [list.capacity], capacity constexpr bool empty() const noexcept; constexpr size_type size() const noexcept; constexpr size_type max_size() const noexcept; constexpr void resize(size_type sz); constexpr void resize(size_type sz, const T& c); // element access constexpr reference front(); constexpr const_reference front() const; constexpr reference back(); constexpr const_reference back() const; // [list.modifiers], modifiers template<class... Args> constexpr reference emplace_front(Args&&... args); template<class... Args> constexpr reference emplace_back(Args&&... args); constexpr void push_front(const T& x); constexpr void push_front(T&& x); template<container-compatible-range<T> R> constexpr void prepend_range(R&& rg); constexpr void pop_front(); constexpr void push_back(const T& x); constexpr void push_back(T&& x); template<container-compatible-range<T> R> constexpr void append_range(R&& rg); constexpr void pop_back(); template<class... Args> constexpr iterator emplace(const_iterator position, Args&&... args); constexpr iterator insert(const_iterator position, const T& x); constexpr iterator insert(const_iterator position, T&& x); constexpr iterator insert(const_iterator position, size_type n, const T& x); template<class InputIterator> constexpr iterator insert(const_iterator position, InputIterator first, InputIterator last); template<container-compatible-range<T> R> constexpr iterator insert_range(const_iterator position, R&& rg); constexpr iterator insert(const_iterator position, initializer_list<T> il); constexpr iterator erase(const_iterator position); constexpr iterator erase(const_iterator position, const_iterator last); constexpr void swap(list&) noexcept(allocator_traits<Allocator>::is_always_equal::value); constexpr void clear() noexcept; // [list.ops], list operations constexpr void splice(const_iterator position, list& x); constexpr void splice(const_iterator position, list&& x); constexpr void splice(const_iterator position, list& x, const_iterator i); constexpr void splice(const_iterator position, list&& x, const_iterator i); constexpr void splice(const_iterator position, list& x, const_iterator first, const_iterator last); constexpr void splice(const_iterator position, list&& x, const_iterator first, const_iterator last); constexpr size_type remove(const T& value); template<class Predicate> constexpr size_type remove_if(Predicate pred); constexpr size_type unique(); template<class BinaryPredicate> constexpr size_type unique(BinaryPredicate binary_pred); constexpr void merge(list& x); constexpr void merge(list&& x); template<class Compare> constexpr void merge(list& x, Compare comp); template<class Compare> constexpr void merge(list&& x, Compare comp); constexpr void sort(); template<class Compare> constexpr void sort(Compare comp); constexpr void reverse() noexcept; }; template<class InputIterator, class Allocator = allocator<iter-value-type<InputIterator>>> list(InputIterator, InputIterator, Allocator = Allocator()) -> list<iter-value-type<InputIterator>, Allocator>; template<ranges::input_range R, class Allocator = allocator<ranges::range_value_t<R>>> list(from_range_t, R&&, Allocator = Allocator()) -> list<ranges::range_value_t<R>, Allocator>; }
4
#
An incomplete type T may be used when instantiating list if the allocator meets the allocator completeness requirements.
T shall be complete before any member of the resulting specialization of list is referenced.
196)196)
These member functions are only provided by containers whose iterators are random access iterators.

23.3.11.2 Constructors, copy, and assignment [list.cons]

🔗
constexpr explicit list(const Allocator&);
1
#
Effects: Constructs an empty list, using the specified allocator.
2
#
Complexity: Constant.
🔗
constexpr explicit list(size_type n, const Allocator& = Allocator());
3
#
Preconditions: T is Cpp17DefaultInsertable into list.
4
#
Effects: Constructs a list with n default-inserted elements using the specified allocator.
5
#
Complexity: Linear in n.
🔗
constexpr list(size_type n, const T& value, const Allocator& = Allocator());
6
#
Preconditions: T is Cpp17CopyInsertable into list.
7
#
Effects: Constructs a list with n copies of value, using the specified allocator.
8
#
Complexity: Linear in n.
🔗
template<class InputIterator> constexpr list(InputIterator first, InputIterator last, const Allocator& = Allocator());
9
#
Effects: Constructs a list equal to the range [first, last).
10
#
Complexity: Linear in distance(first, last).
🔗
template<container-compatible-range<T> R> constexpr list(from_range_t, R&& rg, const Allocator& = Allocator());
11
#
Effects: Constructs a list object with the elements of the range rg.
12
#
Complexity: Linear in ranges​::​distance(rg).

23.3.11.3 Capacity [list.capacity]

🔗
constexpr void resize(size_type sz);
1
#
Preconditions: T is Cpp17DefaultInsertable into list.
2
#
Effects: If size() < sz, appends sz - size() default-inserted elements to the sequence.
If sz <= size(), equivalent to: list<T>::iterator it = begin(); advance(it, sz); erase(it, end());
🔗
constexpr void resize(size_type sz, const T& c);
3
#
Preconditions: T is Cpp17CopyInsertable into list.
4
#
Effects: As if by: if (sz > size()) insert(end(), sz-size(), c); else if (sz < size()) { iterator i = begin(); advance(i, sz); erase(i, end()); } else ; // do nothing

23.3.11.4 Modifiers [list.modifiers]

🔗
constexpr iterator insert(const_iterator position, const T& x); constexpr iterator insert(const_iterator position, T&& x); constexpr iterator insert(const_iterator position, size_type n, const T& x); template<class InputIterator> constexpr iterator insert(const_iterator position, InputIterator first, InputIterator last); template<container-compatible-range<T> R> constexpr iterator insert_range(const_iterator position, R&& rg); constexpr iterator insert(const_iterator position, initializer_list<T>); template<class... Args> constexpr reference emplace_front(Args&&... args); template<class... Args> constexpr reference emplace_back(Args&&... args); template<class... Args> constexpr iterator emplace(const_iterator position, Args&&... args); constexpr void push_front(const T& x); constexpr void push_front(T&& x); template<container-compatible-range<T> R> constexpr void prepend_range(R&& rg); constexpr void push_back(const T& x); constexpr void push_back(T&& x); template<container-compatible-range<T> R> constexpr void append_range(R&& rg);
1
#
Complexity: Insertion of a single element into a list takes constant time and exactly one call to a constructor of T.
Insertion of multiple elements into a list is linear in the number of elements inserted, and the number of calls to the copy constructor or move constructor of T is exactly equal to the number of elements inserted.
2
#
Remarks: Does not affect the validity of iterators and references.
If an exception is thrown, there are no effects.
🔗
constexpr iterator erase(const_iterator position); constexpr iterator erase(const_iterator first, const_iterator last); constexpr void pop_front(); constexpr void pop_back(); constexpr void clear() noexcept;
3
#
Effects: Invalidates only the iterators and references to the erased elements.
4
#
Throws: Nothing.
5
#
Complexity: Erasing a single element is a constant time operation with a single call to the destructor of T.
Erasing a range in a list is linear time in the size of the range and the number of calls to the destructor of type T is exactly equal to the size of the range.

23.3.11.5 Operations [list.ops]

1
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Since lists allow fast insertion and erasing from the middle of a list, certain operations are provided specifically for them.197
In this subclause, arguments for a template parameter named Predicate or BinaryPredicate shall meet the corresponding requirements in [algorithms.requirements].
The semantics of i + n and i - n, where i is an iterator into the list and n is an integer, are the same as those of next(i, n) and prev(i, n), respectively.
For merge and sort, the definitions and requirements in [alg.sorting] apply.
2
#
list provides three splice operations that destructively move elements from one list to another.
The behavior of splice operations is undefined if get_allocator() != x.get_allocator().
🔗
constexpr void splice(const_iterator position, list& x); constexpr void splice(const_iterator position, list&& x);
3
#
Preconditions: addressof(x) != this is true.
4
#
Effects: Inserts the contents of x before position and x becomes empty.
Pointers and references to the moved elements of x now refer to those same elements but as members of *this.
Iterators referring to the moved elements will continue to refer to their elements, but they now behave as iterators into *this, not into x.
5
#
Throws: Nothing.
6
#
Complexity: Constant time.
🔗
constexpr void splice(const_iterator position, list& x, const_iterator i); constexpr void splice(const_iterator position, list&& x, const_iterator i);
7
#
Preconditions: i is a valid dereferenceable iterator of x.
8
#
Effects: Inserts an element pointed to by i from list x before position and removes the element from x.
The result is unchanged if position == i or position == ++i.
Pointers and references to *i continue to refer to this same element but as a member of *this.
Iterators to *i (including i itself) continue to refer to the same element, but now behave as iterators into *this, not into x.
9
#
Throws: Nothing.
10
#
Complexity: Constant time.
🔗
constexpr void splice(const_iterator position, list& x, const_iterator first, const_iterator last); constexpr void splice(const_iterator position, list&& x, const_iterator first, const_iterator last);
11
#
Preconditions: [first, last) is a valid range in x.
position is not an iterator in the range [first, last).
12
#
Effects: Inserts elements in the range [first, last) before position and removes the elements from x.
Pointers and references to the moved elements of x now refer to those same elements but as members of *this.
Iterators referring to the moved elements will continue to refer to their elements, but they now behave as iterators into *this, not into x.
13
#
Throws: Nothing.
14
#
Complexity: Constant time if addressof(x) == this; otherwise, linear time.
🔗
constexpr size_type remove(const T& value); template<class Predicate> constexpr size_type remove_if(Predicate pred);
15
#
Effects: Erases all the elements in the list referred to by a list iterator i for which the following conditions hold: *i == value, pred(*i) != false.
Invalidates only the iterators and references to the erased elements.
16
#
Returns: The number of elements erased.
17
#
Throws: Nothing unless an exception is thrown by *i == value or pred(*i) != false.
18
#
Complexity: Exactly size() applications of the corresponding predicate.
19
#
Remarks: Stable.
🔗
constexpr size_type unique(); template<class BinaryPredicate> constexpr size_type unique(BinaryPredicate binary_pred);
20
#
Let binary_pred be equal_to<>{} for the first overload.
21
#
Preconditions: binary_pred is an equivalence relation.
22
#
Effects: Erases all but the first element from every consecutive group of equivalent elements.
That is, for a nonempty list, erases all elements referred to by the iterator i in the range [begin() + 1, end()) for which binary_pred(*i, *(i - 1)) is true.
Invalidates only the iterators and references to the erased elements.
23
#
Returns: The number of elements erased.
24
#
Throws: Nothing unless an exception is thrown by the predicate.
25
#
Complexity: If empty() is false, exactly size() - 1 applications of the corresponding predicate, otherwise no applications of the predicate.
🔗
constexpr void merge(list& x); constexpr void merge(list&& x); template<class Compare> constexpr void merge(list& x, Compare comp); template<class Compare> constexpr void merge(list&& x, Compare comp);
26
#
Let comp be less<> for the first two overloads.
27
#
Preconditions: *this and x are both sorted with respect to the comparator comp, and get_allocator() == x.get_allocator() is true.
28
#
Effects: If addressof(x) == this, there are no effects.
Otherwise, merges the two sorted ranges [begin(), end()) and [x.begin(), x.end()).
The result is a range that is sorted with respect to the comparator comp.
Pointers and references to the moved elements of x now refer to those same elements but as members of *this.
Iterators referring to the moved elements will continue to refer to their elements, but they now behave as iterators into *this, not into x.
29
#
Complexity: At most size() + x.size() - 1 comparisons if addressof(x) != this; otherwise, no comparisons are performed.
30
#
Remarks: Stable ([algorithm.stable]).
If addressof(x) != this, x is empty after the merge.
No elements are copied by this operation.
If an exception is thrown other than by a comparison, there are no effects.
🔗
constexpr void reverse() noexcept;
31
#
Effects: Reverses the order of the elements in the list.
Does not affect the validity of iterators and references.
32
#
Complexity: Linear time.
🔗
void sort(); template<class Compare> void sort(Compare comp);
33
#
Effects: Sorts the list according to the operator< or a Compare function object.
If an exception is thrown, the order of the elements in *this is unspecified.
Does not affect the validity of iterators and references.
34
#
Complexity: Approximately comparisons, where N == size().
35
#
Remarks: Stable.
197)197)
As specified in [allocator.requirements], the requirements in this Clause apply only to lists whose allocators compare equal.

23.3.11.6 Erasure [list.erasure]

🔗
template<class T, class Allocator, class U = T> typename list<T, Allocator>::size_type constexpr erase(list<T, Allocator>& c, const U& value);
1
#
Effects: Equivalent to: return erase_if(c, [&](const auto& elem) -> bool { return elem == value; });
🔗
template<class T, class Allocator, class Predicate> typename list<T, Allocator>::size_type constexpr erase_if(list<T, Allocator>& c, Predicate pred);
2
#
Effects: Equivalent to: return c.remove_if(pred);

23.3.12 Header <vector> synopsis [vector.syn]

🔗
#include <compare> // see [compare.syn] #include <initializer_list> // see [initializer.list.syn] namespace std { // [vector], class template vector template<class T, class Allocator = allocator<T>> class vector; template<class T, class Allocator> constexpr bool operator==(const vector<T, Allocator>& x, const vector<T, Allocator>& y); template<class T, class Allocator> constexpr synth-three-way-result<T> operator<=>(const vector<T, Allocator>& x, const vector<T, Allocator>& y); template<class T, class Allocator> constexpr void swap(vector<T, Allocator>& x, vector<T, Allocator>& y) noexcept(noexcept(x.swap(y))); // [vector.erasure], erasure template<class T, class Allocator, class U = T> constexpr typename vector<T, Allocator>::size_type erase(vector<T, Allocator>& c, const U& value); template<class T, class Allocator, class Predicate> constexpr typename vector<T, Allocator>::size_type erase_if(vector<T, Allocator>& c, Predicate pred); namespace pmr { template<class T> using vector = std::vector<T, polymorphic_allocator<T>>; } // [vector.bool], specialization of vector for bool // [vector.bool.pspc], partial class template specialization vector<bool, Allocator> template<class Allocator> class vector<bool, Allocator>; template<class T> constexpr bool is-vector-bool-reference = see below; // exposition only // hash support template<class T> struct hash; template<class Allocator> struct hash<vector<bool, Allocator>>; // [vector.bool.fmt], formatter specialization for vector<bool> template<class T, class charT> requires is-vector-bool-reference<T> struct formatter<T, charT>; }

23.3.13 Class template vector [vector]

23.3.13.1 Overview [vector.overview]

1
#
A vector is a sequence container that supports (amortized) constant time insert and erase operations at the end; insert and erase in the middle take linear time.
Storage management is handled automatically, though hints can be given to improve efficiency.
2
#
A vector meets all of the requirements of a container ([container.reqmts]), of a reversible container ([container.rev.reqmts]), of an allocator-aware container ([container.alloc.reqmts]), of a sequence container, including most of the optional sequence container requirements ([sequence.reqmts]), and, for an element type other than bool, of a contiguous container.
The exceptions are the push_front, prepend_range, pop_front, and emplace_front member functions, which are not provided.
Descriptions are provided here only for operations on vector that are not described in one of these tables or for operations where there is additional semantic information.
3
#
The types iterator and const_iterator meet the constexpr iterator requirements ([iterator.requirements.general]).
namespace std { template<class T, class Allocator = allocator<T>> class vector { public: // types using value_type = T; using allocator_type = Allocator; using pointer = typename allocator_traits<Allocator>::pointer; using const_pointer = typename allocator_traits<Allocator>::const_pointer; using reference = value_type&; using const_reference = const value_type&; using size_type = implementation-defined; // see [container.requirements] using difference_type = implementation-defined; // see [container.requirements] using iterator = implementation-defined; // see [container.requirements] using const_iterator = implementation-defined; // see [container.requirements] using reverse_iterator = std::reverse_iterator<iterator>; using const_reverse_iterator = std::reverse_iterator<const_iterator>; // [vector.cons], construct/copy/destroy constexpr vector() noexcept(noexcept(Allocator())) : vector(Allocator()) { } constexpr explicit vector(const Allocator&) noexcept; constexpr explicit vector(size_type n, const Allocator& = Allocator()); constexpr vector(size_type n, const T& value, const Allocator& = Allocator()); template<class InputIterator> constexpr vector(InputIterator first, InputIterator last, const Allocator& = Allocator()); template<container-compatible-range<T> R> constexpr vector(from_range_t, R&& rg, const Allocator& = Allocator()); constexpr vector(const vector& x); constexpr vector(vector&&) noexcept; constexpr vector(const vector&, const type_identity_t<Allocator>&); constexpr vector(vector&&, const type_identity_t<Allocator>&); constexpr vector(initializer_list<T>, const Allocator& = Allocator()); constexpr ~vector(); constexpr vector& operator=(const vector& x); constexpr vector& operator=(vector&& x) noexcept(allocator_traits<Allocator>::propagate_on_container_move_assignment::value || allocator_traits<Allocator>::is_always_equal::value); constexpr vector& operator=(initializer_list<T>); template<class InputIterator> constexpr void assign(InputIterator first, InputIterator last); template<container-compatible-range<T> R> constexpr void assign_range(R&& rg); constexpr void assign(size_type n, const T& u); constexpr void assign(initializer_list<T>); constexpr allocator_type get_allocator() const noexcept; // iterators constexpr iterator begin() noexcept; constexpr const_iterator begin() const noexcept; constexpr iterator end() noexcept; constexpr const_iterator end() const noexcept; constexpr reverse_iterator rbegin() noexcept; constexpr const_reverse_iterator rbegin() const noexcept; constexpr reverse_iterator rend() noexcept; constexpr const_reverse_iterator rend() const noexcept; constexpr const_iterator cbegin() const noexcept; constexpr const_iterator cend() const noexcept; constexpr const_reverse_iterator crbegin() const noexcept; constexpr const_reverse_iterator crend() const noexcept; // [vector.capacity], capacity constexpr bool empty() const noexcept; constexpr size_type size() const noexcept; constexpr size_type max_size() const noexcept; constexpr size_type capacity() const noexcept; constexpr void resize(size_type sz); constexpr void resize(size_type sz, const T& c); constexpr void reserve(size_type n); constexpr void shrink_to_fit(); // element access constexpr reference operator[](size_type n); constexpr const_reference operator[](size_type n) const; constexpr reference at(size_type n); constexpr const_reference at(size_type n) const; constexpr reference front(); constexpr const_reference front() const; constexpr reference back(); constexpr const_reference back() const; // [vector.data], data access constexpr T* data() noexcept; constexpr const T* data() const noexcept; // [vector.modifiers], modifiers template<class... Args> constexpr reference emplace_back(Args&&... args); constexpr void push_back(const T& x); constexpr void push_back(T&& x); template<container-compatible-range<T> R> constexpr void append_range(R&& rg); constexpr void pop_back(); template<class... Args> constexpr iterator emplace(const_iterator position, Args&&... args); constexpr iterator insert(const_iterator position, const T& x); constexpr iterator insert(const_iterator position, T&& x); constexpr iterator insert(const_iterator position, size_type n, const T& x); template<class InputIterator> constexpr iterator insert(const_iterator position, InputIterator first, InputIterator last); template<container-compatible-range<T> R> constexpr iterator insert_range(const_iterator position, R&& rg); constexpr iterator insert(const_iterator position, initializer_list<T> il); constexpr iterator erase(const_iterator position); constexpr iterator erase(const_iterator first, const_iterator last); constexpr void swap(vector&) noexcept(allocator_traits<Allocator>::propagate_on_container_swap::value || allocator_traits<Allocator>::is_always_equal::value); constexpr void clear() noexcept; }; template<class InputIterator, class Allocator = allocator<iter-value-type<InputIterator>>> vector(InputIterator, InputIterator, Allocator = Allocator()) -> vector<iter-value-type<InputIterator>, Allocator>; template<ranges::input_range R, class Allocator = allocator<ranges::range_value_t<R>>> vector(from_range_t, R&&, Allocator = Allocator()) -> vector<ranges::range_value_t<R>, Allocator>; }
4
#
An incomplete type T may be used when instantiating vector if the allocator meets the allocator completeness requirements.
T shall be complete before any member of the resulting specialization of vector is referenced.

23.3.13.2 Constructors [vector.cons]

🔗
constexpr explicit vector(const Allocator&) noexcept;
1
#
Effects: Constructs an empty vector, using the specified allocator.
2
#
Complexity: Constant.
🔗
constexpr explicit vector(size_type n, const Allocator& = Allocator());
3
#
Preconditions: T is Cpp17DefaultInsertable into vector.
4
#
Effects: Constructs a vector with n default-inserted elements using the specified allocator.
5
#
Complexity: Linear in n.
🔗
constexpr vector(size_type n, const T& value, const Allocator& = Allocator());
6
#
Preconditions: T is Cpp17CopyInsertable into vector.
7
#
Effects: Constructs a vector with n copies of value, using the specified allocator.
8
#
Complexity: Linear in n.
🔗
template<class InputIterator> constexpr vector(InputIterator first, InputIterator last, const Allocator& = Allocator());
9
#
Effects: Constructs a vector equal to the range [first, last), using the specified allocator.
10
#
Complexity: Makes only N calls to the copy constructor of T (where N is the distance between first and last) and no reallocations if iterators first and last are of forward, bidirectional, or random access categories.
It makes order N calls to the copy constructor of T and order reallocations if they are just input iterators.
🔗
template<container-compatible-range<T> R> constexpr vector(from_range_t, R&& rg, const Allocator& = Allocator());
11
#
Effects: Constructs a vector object with the elements of the range rg, using the specified allocator.
12
#
Complexity: Initializes exactly N elements from the results of dereferencing successive iterators of rg, where N is ranges​::​distance(rg).
13
#
Performs no reallocations if:
Otherwise, performs order reallocations and order N calls to the copy or move constructor of T.

23.3.13.3 Capacity [vector.capacity]

🔗
constexpr size_type capacity() const noexcept;
1
#
Returns: The total number of elements that the vector can hold without requiring reallocation.
2
#
Complexity: Constant time.
🔗
constexpr void reserve(size_type n);
3
#
Preconditions: T is Cpp17MoveInsertable into vector.
4
#
Effects: A directive that informs a vector of a planned change in size, so that it can manage the storage allocation accordingly.
After reserve(), capacity() is greater or equal to the argument of reserve if reallocation happens; and equal to the previous value of capacity() otherwise.
Reallocation happens at this point if and only if the current capacity is less than the argument of reserve().
If an exception is thrown other than by the move constructor of a non-Cpp17CopyInsertable type, there are no effects.
5
#
Throws: length_error if n > max_size().198
6
#
Complexity: It does not change the size of the sequence and takes at most linear time in the size of the sequence.
7
#
Remarks: Reallocation invalidates all the references, pointers, and iterators referring to the elements in the sequence, as well as the past-the-end iterator.
[Note 1: 
If no reallocation happens, they remain valid.
— end note]
No reallocation shall take place during insertions that happen after a call to reserve() until an insertion would make the size of the vector greater than the value of capacity().
🔗
constexpr void shrink_to_fit();
8
#
Preconditions: T is Cpp17MoveInsertable into vector.
9
#
Effects: shrink_to_fit is a non-binding request to reduce capacity() to size().
[Note 2: 
The request is non-binding to allow latitude for implementation-specific optimizations.
— end note]
It does not increase capacity(), but may reduce capacity() by causing reallocation.
If an exception is thrown other than by the move constructor of a non-Cpp17CopyInsertable T, there are no effects.
10
#
Complexity: If reallocation happens, linear in the size of the sequence.
11
#
Remarks: Reallocation invalidates all the references, pointers, and iterators referring to the elements in the sequence as well as the past-the-end iterator.
[Note 3: 
If no reallocation happens, they remain valid.
— end note]
🔗
constexpr void swap(vector& x) noexcept(allocator_traits<Allocator>::propagate_on_container_swap::value || allocator_traits<Allocator>::is_always_equal::value);
12
#
Effects: Exchanges the contents and capacity() of *this with that of x.
13
#
Complexity: Constant time.
🔗
constexpr void resize(size_type sz);
14
#
Preconditions: T is Cpp17MoveInsertable and Cpp17DefaultInsertable into vector.
15
#
Effects: If sz < size(), erases the last size() - sz elements from the sequence.
Otherwise, appends sz - size() default-inserted elements to the sequence.
16
#
Remarks: If an exception is thrown other than by the move constructor of a non-Cpp17CopyInsertable T, there are no effects.
🔗
constexpr void resize(size_type sz, const T& c);
17
#
Preconditions: T is Cpp17CopyInsertable into vector.
18
#
Effects: If sz < size(), erases the last size() - sz elements from the sequence.
Otherwise, appends sz - size() copies of c to the sequence.
19
#
Remarks: If an exception is thrown, there are no effects.
198)198)
reserve() uses Allocator​::​allocate() which can throw an appropriate exception.

23.3.13.4 Data [vector.data]

🔗
constexpr T* data() noexcept; constexpr const T* data() const noexcept;
1
#
Returns: A pointer such that [data(), data() + size()) is a valid range.
For a non-empty vector, data() == addressof(front()) is true.
2
#
Complexity: Constant time.

23.3.13.5 Modifiers [vector.modifiers]

🔗
constexpr iterator insert(const_iterator position, const T& x); constexpr iterator insert(const_iterator position, T&& x); constexpr iterator insert(const_iterator position, size_type n, const T& x); template<class InputIterator> constexpr iterator insert(const_iterator position, InputIterator first, InputIterator last); template<container-compatible-range<T> R> constexpr iterator insert_range(const_iterator position, R&& rg); constexpr iterator insert(const_iterator position, initializer_list<T>); template<class... Args> constexpr reference emplace_back(Args&&... args); template<class... Args> constexpr iterator emplace(const_iterator position, Args&&... args); constexpr void push_back(const T& x); constexpr void push_back(T&& x); template<container-compatible-range<T> R> constexpr void append_range(R&& rg);
1
#
Complexity: If reallocation happens, linear in the number of elements of the resulting vector; otherwise, linear in the number of elements inserted plus the distance to the end of the vector.
2
#
Remarks: Causes reallocation if the new size is greater than the old capacity.
Reallocation invalidates all the references, pointers, and iterators referring to the elements in the sequence, as well as the past-the-end iterator.
If no reallocation happens, then references, pointers, and iterators before the insertion point remain valid but those at or after the insertion point, including the past-the-end iterator, are invalidated.
If an exception is thrown other than by the copy constructor, move constructor, assignment operator, or move assignment operator of T or by any InputIterator operation, there are no effects.
If an exception is thrown while inserting a single element at the end and T is Cpp17CopyInsertable or is_nothrow_move_constructible_v<T> is true, there are no effects.
Otherwise, if an exception is thrown by the move constructor of a non-Cpp17CopyInsertable T, the effects are unspecified.
3
#
For the declarations taking a range R, performs at most one reallocation if:
For the declarations taking a pair of InputIterator, performs at most one reallocation if InputIterator models Cpp17ForwardIterator.
🔗
constexpr iterator erase(const_iterator position); constexpr iterator erase(const_iterator first, const_iterator last); constexpr void pop_back();
4
#
Effects: Invalidates iterators and references at or after the point of the erase.
5
#
Throws: Nothing unless an exception is thrown by the assignment operator or move assignment operator of T.
6
#
Complexity: The destructor of T is called the number of times equal to the number of the elements erased, but the assignment operator of T is called the number of times equal to the number of elements in the vector after the erased elements.

23.3.13.6 Erasure [vector.erasure]

🔗
template<class T, class Allocator, class U = T> constexpr typename vector<T, Allocator>::size_type erase(vector<T, Allocator>& c, const U& value);
1
#
Effects: Equivalent to: auto it = remove(c.begin(), c.end(), value); auto r = distance(it, c.end()); c.erase(it, c.end()); return r;
🔗
template<class T, class Allocator, class Predicate> constexpr typename vector<T, Allocator>::size_type erase_if(vector<T, Allocator>& c, Predicate pred);
2
#
Effects: Equivalent to: auto it = remove_if(c.begin(), c.end(), pred); auto r = distance(it, c.end()); c.erase(it, c.end()); return r;

23.3.14 Specialization of vector for bool [vector.bool]

23.3.14.1 Partial class template specialization vector<bool, Allocator> [vector.bool.pspc]

1
#
To optimize space allocation, a partial specialization of vector for bool elements is provided: namespace std { template<class Allocator> class vector<bool, Allocator> { public: // types using value_type = bool; using allocator_type = Allocator; using pointer = implementation-defined; using const_pointer = implementation-defined; using const_reference = bool; using size_type = implementation-defined; // see [container.requirements] using difference_type = implementation-defined; // see [container.requirements] using iterator = implementation-defined; // see [container.requirements] using const_iterator = implementation-defined; // see [container.requirements] using reverse_iterator = std::reverse_iterator<iterator>; using const_reverse_iterator = std::reverse_iterator<const_iterator>; // bit reference class reference { public: constexpr reference(const reference&) = default; constexpr ~reference(); constexpr operator bool() const noexcept; constexpr reference& operator=(bool x) noexcept; constexpr reference& operator=(const reference& x) noexcept; constexpr const reference& operator=(bool x) const noexcept; constexpr void flip() noexcept; // flips the bit }; // construct/copy/destroy constexpr vector() noexcept(noexcept(Allocator())) : vector(Allocator()) { } constexpr explicit vector(const Allocator&) noexcept; constexpr explicit vector(size_type n, const Allocator& = Allocator()); constexpr vector(size_type n, const bool& value, const Allocator& = Allocator()); template<class InputIterator> constexpr vector(InputIterator first, InputIterator last, const Allocator& = Allocator()); template<container-compatible-range<bool> R> constexpr vector(from_range_t, R&& rg, const Allocator& = Allocator()); constexpr vector(const vector& x); constexpr vector(vector&& x) noexcept; constexpr vector(const vector&, const type_identity_t<Allocator>&); constexpr vector(vector&&, const type_identity_t<Allocator>&); constexpr vector(initializer_list<bool>, const Allocator& = Allocator()); constexpr ~vector(); constexpr vector& operator=(const vector& x); constexpr vector& operator=(vector&& x) noexcept(allocator_traits<Allocator>::propagate_on_container_move_assignment::value || allocator_traits<Allocator>::is_always_equal::value); constexpr vector& operator=(initializer_list<bool>); template<class InputIterator> constexpr void assign(InputIterator first, InputIterator last); template<container-compatible-range<bool> R> constexpr void assign_range(R&& rg); constexpr void assign(size_type n, const bool& t); constexpr void assign(initializer_list<bool>); constexpr allocator_type get_allocator() const noexcept; // iterators constexpr iterator begin() noexcept; constexpr const_iterator begin() const noexcept; constexpr iterator end() noexcept; constexpr const_iterator end() const noexcept; constexpr reverse_iterator rbegin() noexcept; constexpr const_reverse_iterator rbegin() const noexcept; constexpr reverse_iterator rend() noexcept; constexpr const_reverse_iterator rend() const noexcept; constexpr const_iterator cbegin() const noexcept; constexpr const_iterator cend() const noexcept; constexpr const_reverse_iterator crbegin() const noexcept; constexpr const_reverse_iterator crend() const noexcept; // capacity constexpr bool empty() const noexcept; constexpr size_type size() const noexcept; constexpr size_type max_size() const noexcept; constexpr size_type capacity() const noexcept; constexpr void resize(size_type sz, bool c = false); constexpr void reserve(size_type n); constexpr void shrink_to_fit(); // element access constexpr reference operator[](size_type n); constexpr const_reference operator[](size_type n) const; constexpr reference at(size_type n); constexpr const_reference at(size_type n) const; constexpr reference front(); constexpr const_reference front() const; constexpr reference back(); constexpr const_reference back() const; // modifiers template<class... Args> constexpr reference emplace_back(Args&&... args); constexpr void push_back(const bool& x); template<container-compatible-range<bool> R> constexpr void append_range(R&& rg); constexpr void pop_back(); template<class... Args> constexpr iterator emplace(const_iterator position, Args&&... args); constexpr iterator insert(const_iterator position, const bool& x); constexpr iterator insert(const_iterator position, size_type n, const bool& x); template<class InputIterator> constexpr iterator insert(const_iterator position, InputIterator first, InputIterator last); template<container-compatible-range<bool> R> constexpr iterator insert_range(const_iterator position, R&& rg); constexpr iterator insert(const_iterator position, initializer_list<bool> il); constexpr iterator erase(const_iterator position); constexpr iterator erase(const_iterator first, const_iterator last); constexpr void swap(vector&) noexcept(allocator_traits<Allocator>::propagate_on_container_swap::value || allocator_traits<Allocator>::is_always_equal::value); static constexpr void swap(reference x, reference y) noexcept; constexpr void flip() noexcept; // flips all bits constexpr void clear() noexcept; }; }
2
#
Unless described below, all operations have the same requirements and semantics as the primary vector template, except that operations dealing with the bool value type map to bit values in the container storage and allocator_traits​::​construct is not used to construct these values.
3
#
There is no requirement that the data be stored as a contiguous allocation of bool values.
A space-optimized representation of bits is recommended instead.
4
#
reference is a class that simulates the behavior of references of a single bit in vector<bool>.
The conversion function returns true when the bit is set, and false otherwise.
The assignment operators set the bit when the argument is (convertible to) true and clear it otherwise.
flip reverses the state of the bit.
🔗
constexpr void flip() noexcept;
5
#
Effects: Replaces each element in the container with its complement.
🔗
static constexpr void swap(reference x, reference y) noexcept;
6
#
Effects: Exchanges the contents of x and y as if by: bool b = x; x = y; y = b;
🔗
template<class Allocator> struct hash<vector<bool, Allocator>>;
7
#
The specialization is enabled ([unord.hash]).
🔗
template<class T> constexpr bool is-vector-bool-reference = see below;
8
#
The expression is-vector-bool-reference<T> is true if T denotes the type vector<bool, Alloc>​::​reference for some type Alloc and vector<bool, Alloc> is not a program-defined specialization.

23.3.14.2 Formatter specialization for vector<bool> [vector.bool.fmt]

🔗
namespace std { template<class T, class charT> requires is-vector-bool-reference<T> struct formatter<T, charT> { private: formatter<bool, charT> underlying_; // exposition only public: template<class ParseContext> constexpr typename ParseContext::iterator parse(ParseContext& ctx); template<class FormatContext> typename FormatContext::iterator format(const T& ref, FormatContext& ctx) const; }; }
🔗
template<class ParseContext> constexpr typename ParseContext::iterator parse(ParseContext& ctx);
1
#
Equivalent to: return underlying_.parse(ctx);
🔗
template<class FormatContext> typename FormatContext::iterator format(const T& ref, FormatContext& ctx) const;
2
#
Equivalent to: return underlying_.format(ref, ctx);

23.3.15 Header <inplace_vector> synopsis [inplace.vector.syn]

🔗
// mostly freestanding #include <compare> // see [compare.syn] #include <initializer_list> // see [initializer.list.syn] namespace std { // [inplace.vector], class template inplace_vector template<class T, size_t N> class inplace_vector; // partially freestanding // [inplace.vector.erasure], erasure template<class T, size_t N, class U = T> constexpr typename inplace_vector<T, N>::size_type erase(inplace_vector<T, N>& c, const U& value); template<class T, size_t N, class Predicate> constexpr typename inplace_vector<T, N>::size_type erase_if(inplace_vector<T, N>& c, Predicate pred); }

23.3.16 Class template inplace_vector [inplace.vector]

23.3.16.1 Overview [inplace.vector.overview]

1
#
An inplace_vector is a contiguous container.
Its capacity is fixed and its elements are stored within the inplace_vector object itself.
2
#
An inplace_vector meets all of the requirements of a container ([container.reqmts]), of a reversible container ([container.rev.reqmts]), of a contiguous container, and of a sequence container, including most of the optional sequence container requirements ([sequence.reqmts]).
The exceptions are the push_front, prepend_range, pop_front, and emplace_front member functions, which are not provided.
Descriptions are provided here only for operations on inplace_vector that are not described in one of these tables or for operations where there is additional semantic information.
3
#
For any N, inplace_vector<T, N>​::​iterator and inplace_vector<T, N>​::​const_iterator meet the constexpr iterator requirements.
4
#
Any member function of inplace_vector<T, N> that would cause the size to exceed N throws an exception of type bad_alloc.
5
#
Let IV denote a specialization of inplace_vector<T, N>.
If N is zero, then IV is trivially copyable and empty, and std​::​is_trivially_default_constructible_v<IV> is true.
Otherwise:
  • (5.1)
    If is_trivially_copy_constructible_v<T> is true, then IV has a trivial copy constructor.
  • (5.2)
    If is_trivially_move_constructible_v<T> is true, then IV has a trivial move constructor.
  • (5.3)
    If is_trivially_destructible_v<T> is true, then:
    • (5.3.1)
      IV has a trivial destructor.
    • (5.3.2)
      If is_trivially_copy_constructible_v<T> && is_trivially_copy_assignable_v<T> is true, then IV has a trivial copy assignment operator.
    • (5.3.3)
      If is_trivially_move_constructible_v<T> && is_trivially_move_assignable_v<T> is true, then IV has a trivial move assignment operator.
namespace std { template<class T, size_t N> class inplace_vector { public: // types: using value_type = T; using pointer = T*; using const_pointer = const T*; using reference = value_type&; using const_reference = const value_type&; using size_type = size_t; using difference_type = ptrdiff_t; using iterator = implementation-defined; // see [container.requirements] using const_iterator = implementation-defined; // see [container.requirements] using reverse_iterator = std::reverse_iterator<iterator>; using const_reverse_iterator = std::reverse_iterator<const_iterator>; // [inplace.vector.cons], construct/copy/destroy constexpr inplace_vector() noexcept; constexpr explicit inplace_vector(size_type n); // freestanding-deleted constexpr inplace_vector(size_type n, const T& value); // freestanding-deleted template<class InputIterator> constexpr inplace_vector(InputIterator first, InputIterator last); // freestanding-deleted template<container-compatible-range<T> R> constexpr inplace_vector(from_range_t, R&& rg); // freestanding-deleted constexpr inplace_vector(const inplace_vector&); constexpr inplace_vector(inplace_vector&&) noexcept(N == 0 || is_nothrow_move_constructible_v<T>); constexpr inplace_vector(initializer_list<T> il); // freestanding-deleted constexpr ~inplace_vector(); constexpr inplace_vector& operator=(const inplace_vector& other); constexpr inplace_vector& operator=(inplace_vector&& other) noexcept(N == 0 || (is_nothrow_move_assignable_v<T> && is_nothrow_move_constructible_v<T>)); constexpr inplace_vector& operator=(initializer_list<T>); // freestanding-deleted template<class InputIterator> constexpr void assign(InputIterator first, InputIterator last); // freestanding-deleted template<container-compatible-range<T> R> constexpr void assign_range(R&& rg); // freestanding-deleted constexpr void assign(size_type n, const T& u); // freestanding-deleted constexpr void assign(initializer_list<T> il); // freestanding-deleted // iterators constexpr iterator begin() noexcept; constexpr const_iterator begin() const noexcept; constexpr iterator end() noexcept; constexpr const_iterator end() const noexcept; constexpr reverse_iterator rbegin() noexcept; constexpr const_reverse_iterator rbegin() const noexcept; constexpr reverse_iterator rend() noexcept; constexpr const_reverse_iterator rend() const noexcept; constexpr const_iterator cbegin() const noexcept; constexpr const_iterator cend() const noexcept; constexpr const_reverse_iterator crbegin() const noexcept; constexpr const_reverse_iterator crend() const noexcept; // [inplace.vector.capacity], size/capacity constexpr bool empty() const noexcept; constexpr size_type size() const noexcept; static constexpr size_type max_size() noexcept; static constexpr size_type capacity() noexcept; constexpr void resize(size_type sz); // freestanding-deleted constexpr void resize(size_type sz, const T& c); // freestanding-deleted static constexpr void reserve(size_type n); // freestanding-deleted static constexpr void shrink_to_fit() noexcept; // element access constexpr reference operator[](size_type n); constexpr const_reference operator[](size_type n) const; constexpr reference at(size_type n); // freestanding-deleted constexpr const_reference at(size_type n) const; // freestanding-deleted constexpr reference front(); constexpr const_reference front() const; constexpr reference back(); constexpr const_reference back() const; // [inplace.vector.data], data access constexpr T* data() noexcept; constexpr const T* data() const noexcept; // [inplace.vector.modifiers], modifiers template<class... Args> constexpr reference emplace_back(Args&&... args); // freestanding-deleted constexpr reference push_back(const T& x); // freestanding-deleted constexpr reference push_back(T&& x); // freestanding-deleted template<container-compatible-range<T> R> constexpr void append_range(R&& rg); // freestanding-deleted constexpr void pop_back(); template<class... Args> constexpr pointer try_emplace_back(Args&&... args); constexpr pointer try_push_back(const T& x); constexpr pointer try_push_back(T&& x); template<container-compatible-range<T> R> constexpr ranges::borrowed_iterator_t<R> try_append_range(R&& rg); template<class... Args> constexpr reference unchecked_emplace_back(Args&&... args); constexpr reference unchecked_push_back(const T& x); constexpr reference unchecked_push_back(T&& x); template<class... Args> constexpr iterator emplace(const_iterator position, Args&&... args); // freestanding-deleted constexpr iterator insert(const_iterator position, const T& x); // freestanding-deleted constexpr iterator insert(const_iterator position, T&& x); // freestanding-deleted constexpr iterator insert(const_iterator position, size_type n, // freestanding-deleted const T& x); template<class InputIterator> constexpr iterator insert(const_iterator position, // freestanding-deleted InputIterator first, InputIterator last); template<container-compatible-range<T> R> constexpr iterator insert_range(const_iterator position, R&& rg); // freestanding-deleted constexpr iterator insert(const_iterator position, // freestanding-deleted initializer_list<T> il); constexpr iterator erase(const_iterator position); constexpr iterator erase(const_iterator first, const_iterator last); constexpr void swap(inplace_vector& x) noexcept(N == 0 || (is_nothrow_swappable_v<T> && is_nothrow_move_constructible_v<T>)); constexpr void clear() noexcept; constexpr friend bool operator==(const inplace_vector& x, const inplace_vector& y); constexpr friend synth-three-way-result<T> operator<=>(const inplace_vector& x, const inplace_vector& y); constexpr friend void swap(inplace_vector& x, inplace_vector& y) noexcept(N == 0 || (is_nothrow_swappable_v<T> && is_nothrow_move_constructible_v<T>)) { x.swap(y); } }; }

23.3.16.2 Constructors [inplace.vector.cons]

🔗
constexpr explicit inplace_vector(size_type n);
1
#
Preconditions: T is Cpp17DefaultInsertable into inplace_vector.
2
#
Effects: Constructs an inplace_vector with n default-inserted elements.
3
#
Complexity: Linear in n.
🔗
constexpr inplace_vector(size_type n, const T& value);
4
#
Preconditions: T is Cpp17CopyInsertable into inplace_vector.
5
#
Effects: Constructs an inplace_vector with n copies of value.
6
#
Complexity: Linear in n.
🔗
template<class InputIterator> constexpr inplace_vector(InputIterator first, InputIterator last);
7
#
Effects: Constructs an inplace_vector equal to the range [first, last).
8
#
Complexity: Linear in distance(first, last).
🔗
template<container-compatible-range<T> R> constexpr inplace_vector(from_range_t, R&& rg);
9
#
Effects: Constructs an inplace_vector with the elements of the range rg.
10
#
Complexity: Linear in ranges​::​distance(rg).

23.3.16.3 Size and capacity [inplace.vector.capacity]

🔗
static constexpr size_type capacity() noexcept; static constexpr size_type max_size() noexcept;
1
#
Returns: N.
🔗
constexpr void resize(size_type sz);
2
#
Preconditions: T is Cpp17DefaultInsertable into inplace_vector.
3
#
Effects: If sz < size(), erases the last size() - sz elements from the sequence.
Otherwise, appends sz - size() default-inserted elements to the sequence.
4
#
Remarks: If an exception is thrown, there are no effects on *this.
🔗
constexpr void resize(size_type sz, const T& c);
5
#
Preconditions: T is Cpp17CopyInsertable into inplace_vector.
6
#
Effects: If sz < size(), erases the last size() - sz elements from the sequence.
Otherwise, appends sz - size() copies of c to the sequence.
7
#
Remarks: If an exception is thrown, there are no effects on *this.

23.3.16.4 Data [inplace.vector.data]

🔗
constexpr T* data() noexcept; constexpr const T* data() const noexcept;
1
#
Returns: A pointer such that [data(), data() + size()) is a valid range.
For a non-empty inplace_vector, data() == addressof(front()) is true.
2
#
Complexity: Constant time.

23.3.16.5 Modifiers [inplace.vector.modifiers]

🔗
constexpr iterator insert(const_iterator position, const T& x); constexpr iterator insert(const_iterator position, T&& x); constexpr iterator insert(const_iterator position, size_type n, const T& x); template<class InputIterator> constexpr iterator insert(const_iterator position, InputIterator first, InputIterator last); template<container-compatible-range<T> R> constexpr iterator insert_range(const_iterator position, R&& rg); constexpr iterator insert(const_iterator position, initializer_list<T> il); template<class... Args> constexpr iterator emplace(const_iterator position, Args&&... args); template<container-compatible-range<T> R> constexpr void append_range(R&& rg);
1
#
Let n be the value of size() before this call for the append_range overload, and distance(begin, position) otherwise.
2
#
Complexity: Linear in the number of elements inserted plus the distance to the end of the vector.
3
#
Remarks: If an exception is thrown other than by the copy constructor, move constructor, assignment operator, or move assignment operator of T or by any InputIterator operation, there are no effects.
Otherwise, if an exception is thrown, then size()  ≥ n and elements in the range begin() + [0, n) are not modified.
🔗
constexpr reference push_back(const T& x); constexpr reference push_back(T&& x); template<class... Args> constexpr reference emplace_back(Args&&... args);
4
#
Returns: back().
5
#
Throws: bad_alloc or any exception thrown by the initialization of the inserted element.
6
#
Complexity: Constant.
7
#
Remarks: If an exception is thrown, there are no effects on *this.
🔗
template<class... Args> constexpr pointer try_emplace_back(Args&&... args); constexpr pointer try_push_back(const T& x); constexpr pointer try_push_back(T&& x);
8
#
Let vals denote a pack:
  • (8.1)
    std​::​forward<Args>(args)... for the first overload,
  • (8.2)
    x for the second overload,
  • (8.3)
    std​::​move(x) for the third overload.
9
#
Preconditions: value_type is Cpp17EmplaceConstructible into inplace_vector from vals....
10
#
Effects: If size() < capacity() is true, appends an object of type T direct-non-list-initialized with vals....
Otherwise, there are no effects.
11
#
Returns: nullptr if size() == capacity() is true, otherwise addressof(back()).
12
#
Throws: Nothing unless an exception is thrown by the initialization of the inserted element.
13
#
Complexity: Constant.
14
#
Remarks: If an exception is thrown, there are no effects on *this.
🔗
template<container-compatible-range<T> R> constexpr ranges::borrowed_iterator_t<R> try_append_range(R&& rg);
15
#
Preconditions: value_type is Cpp17EmplaceConstructible into inplace_vector from
*ranges​::​begin(rg).
16
#
Effects: Appends copies of initial elements in rg before end(), until all elements are inserted or size() == capacity() is true.
Each iterator in the range rg is dereferenced at most once.
17
#
Returns: An iterator pointing to the first element of rg that was not inserted into *this, or ranges​::​end(rg) if no such element exists.
18
#
Complexity: Linear in the number of elements inserted.
19
#
Remarks: Let n be the value of size() prior to this call.
If an exception is thrown after the insertion of k elements, then size() equals , elements in the range begin() + [0, n) are not modified, and elements in the range begin() + [n, ) correspond to the inserted elements.
🔗
template<class... Args> constexpr reference unchecked_emplace_back(Args&&... args);
20
#
Preconditions: size() < capacity() is true.
21
#
Effects: Equivalent to: return *try_emplace_back(std​::​forward<Args>(args)...);
🔗
constexpr reference unchecked_push_back(const T& x); constexpr reference unchecked_push_back(T&& x);
22
#
Preconditions: size() < capacity() is true.
23
#
Effects: Equivalent to: return *try_push_back(std​::​forward<decltype(x)>(x));
🔗
static constexpr void reserve(size_type n);
24
#
Effects: None.
25
#
Throws: bad_alloc if n > capacity() is true.
🔗
static constexpr void shrink_to_fit() noexcept;
26
#
Effects: None.
🔗
constexpr iterator erase(const_iterator position); constexpr iterator erase(const_iterator first, const_iterator last); constexpr void pop_back();
27
#
Effects: Invalidates iterators and references at or after the point of the erase.
28
#
Throws: Nothing unless an exception is thrown by the assignment operator or move assignment operator of T.
29
#
Complexity: The destructor of T is called the number of times equal to the number of the elements erased, but the assignment operator of T is called the number of times equal to the number of elements after the erased elements.

23.3.16.6 Erasure [inplace.vector.erasure]

🔗
template<class T, size_t N, class U = T> constexpr size_t erase(inplace_vector<T, N>& c, const U& value);
1
#
Effects: Equivalent to: auto it = remove(c.begin(), c.end(), value); auto r = distance(it, c.end()); c.erase(it, c.end()); return r;
🔗
template<class T, size_t N, class Predicate> constexpr size_t erase_if(inplace_vector<T, N>& c, Predicate pred);
2
#
Effects: Equivalent to: auto it = remove_if(c.begin(), c.end(), pred); auto r = distance(it, c.end()); c.erase(it, c.end()); return r;