Standard library header <vector>

 

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Standard library headers

Language support <cfloat> <climits> <compare> (C++20) <contracts> (C++26) <coroutine> (C++20) <csetjmp> <csignal> <cstdarg> <cstddef> <cstdint> (C++11) <cstdlib> <exception> <initializer_list> (C++11)    <limits> <new> <source_location> (C++20) <stdfloat> (C++23) <typeinfo> <version> (C++20) Concepts <concepts> (C++20) Diagnostics <cassert> <cerrno> <debugging> (C++26) <stacktrace> (C++23) <stdexcept> <system_error> (C++11) Memory management <memory> <memory_resource> (C++17) <scoped_allocator> (C++11) Metaprogramming <type_traits> (C++11) <ratio> (C++11)

General utilities <any> (C++17) <bitset> <bit> (C++20) <charconv> (C++17) <expected> (C++23) <format> (C++20) <functional> <optional> (C++17) <stdbit.h> (C++26) <tuple> (C++11) <typeindex> (C++11) <utility> <variant> (C++17) Containers <array> (C++11) <deque> <flat_map> (C++23) <flat_set> (C++23) <forward_list> (C++11) <hive> (C++26) <inplace_vector> (C++26)    <list> <map> <mdspan> (C++23) <queue> <set> <span> (C++20) <stack> <unordered_map> (C++11) <unordered_set> (C++11) <vector> Iterators <iterator> Ranges <generator> (C++23) <ranges> (C++20)

Algorithms <algorithm> <numeric> Strings <cctype> <cstring> <cuchar> (C++11) <cwchar> <cwctype> <string_view> (C++17) <string> Text processing <clocale> <codecvt> (C++11/17/26*) <locale> <regex> (C++11) <text_encoding> (C++26)    Numerics <cfenv> (C++11) <cmath> <complex> <linalg> (C++26) <numbers> (C++20) <random> (C++11) <simd> (C++26) <stdckdint.h> (C++26) <valarray> Time <chrono> (C++11) <ctime> C compatibility <ccomplex> (C++11/17/20*) <ciso646> (until C++20) <cstdalign> (C++11/17/20*) <cstdbool> (C++11/17/20*) <ctgmath> (C++11/17/20*)

Input/output <cinttypes> (C++11) <cstdio> <filesystem> (C++17) <fstream> <iomanip> <iosfwd> <iostream> <ios> <istream> <ostream> <print> (C++23) <spanstream> (C++23) <sstream> <streambuf> <strstream> (C++98/26*) <syncstream> (C++20) Concurrency support <atomic> (C++11) <barrier> (C++20) <condition_variable> (C++11) <future> (C++11) <hazard_pointer> (C++26) <latch> (C++20) <mutex> (C++11) <rcu> (C++26) <semaphore> (C++20) <shared_mutex> (C++14) <stdatomic.h> (C++23) <stop_token> (C++20) <thread> (C++11) Execution support <execution> (C++17)

 

See More

This header is part of the containers library.

Includes
<compare> (C++20)	Three-way comparison operator support
<initializer_list> (C++11)	std::initializer_list class template
Classes
vector	resizable contiguous array (class template)
vector<bool>	space-efficient dynamic bitset (class template specialization)
std::hash<std::vector<bool>> (C++11)	hash support for std::vector<bool> (class template specialization)
Forward declarations
Defined in header <functional>
hash (C++11)	hash function object (class template)
Functions
operator==operator!=operator<operator<=operator>operator>=operator<=> (removed in C++20)(removed in C++20)(removed in C++20)(removed in C++20)(removed in C++20)(C++20)	lexicographically compares the values of two vectors (function template)
std::swap(std::vector)	specializes the std::swap algorithm (function template)
erase(std::vector)erase_if(std::vector) (C++20)	erases all elements satisfying specific criteria (function template)
Range access
begincbegin (C++11)(C++14)	returns an iterator to the beginning of a container or array (function template)
endcend (C++11)(C++14)	returns an iterator to the end of a container or array (function template)
rbegincrbegin (C++14)	returns a reverse iterator to the beginning of a container or array (function template)
rendcrend (C++14)	returns a reverse end iterator for a container or array (function template)
sizessize (C++17)(C++20)	returns the size of a container or array (function template)
empty (C++17)	checks whether the container is empty (function template)
data (C++17)	obtains the pointer to the underlying array (function template)

Synopsis

#include <compare>
#include <initializer_list>

namespace std {
  // 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)));

  // 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>>;
  }

  // specialization of vector for bool
  // partial class template specialization vector<bool, Allocator>
  template<class Allocator>
  class vector<bool, Allocator>;

  template<class T>
  constexpr bool /*is-vector-bool-reference*/ = /* see description */; // exposition only

  // hash support
  template<class T>
  struct hash;
  template<class Allocator>
  struct hash<vector<bool, Allocator>>;

  // formatter specialization for vector<bool>
  template<class T, class CharT>
    requires /*is-vector-bool-reference*/<T>
  struct formatter<T, CharT>;
}

Class template std::vector

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 */;
    using difference_type        = /* implementation-defined */;
    using iterator               = /* implementation-defined */;
    using const_iterator         = /* implementation-defined */;
    using reverse_iterator       = std::reverse_iterator<iterator>;
    using const_reverse_iterator = std::reverse_iterator<const_iterator>;

    // 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 InputIter>
    constexpr vector(InputIter first, InputIter 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 InputIter>
    constexpr void assign(InputIter first, InputIter 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;

    // 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 const_reference at(size_type n) const;
    constexpr reference at(size_type n);
    constexpr reference front();
    constexpr const_reference front() const;
    constexpr reference back();
    constexpr const_reference back() const;

    // data access
    constexpr T* data() noexcept;
    constexpr const T* data() const noexcept;

    // 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 InputIter>
    constexpr iterator insert(const_iterator position, InputIter first, InputIter 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 InputIter, class Allocator = allocator</*iter-value-type*/<InputIter>>>
  vector(InputIter, InputIter, Allocator = Allocator())
    -> vector</*iter-value-type*/<InputIter>, 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>;
}

Class template std::vector specialization for bool

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 */;
    using difference_type        = /* implementation-defined */;
    using iterator               = /* implementation-defined */;
    using const_iterator         = /* implementation-defined */;
    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 InputIter>
    constexpr vector(InputIter first, InputIter 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 InputIter>
    constexpr void assign(InputIter first, InputIter 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 const_reference at(size_type n) const;
    constexpr reference at(size_type n);
    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 InputIter>
    constexpr iterator insert(const_iterator position, InputIter first, InputIter 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;
  };
}

Class template std::formatter specialization for std::vector<bool>::reference

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;
  };
}

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 4140	C++98	the synopsis contains a declaration of the default constructor of std::vector<bool, Alloc>::reference	removed the declaration