# <vector>

<head><title>&lt;vector&gt;</title></head>

# `<vector>`

* * *

Include the [STL](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_index.html#STL)
standard header **`<vector>`** to define the
[container](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_lib_cont.html#Containers)
template class `vector` and several supporting
templates.

    namespace std {
    template<class Ty, class Alloc>
        class vector;
    template<class Alloc>
        class vector<bool>;
    
            // TEMPLATE FUNCTIONS
    template<class Ty, class Alloc>
        bool operator==(
            const vector<Ty, Alloc>& left,
            const vector<Ty, Alloc>& right);
    template<class Ty, class Alloc>
        bool operator!=(
            const vector<Ty, Alloc>& left,
            const vector<Ty, Alloc>& right);
    template<class Ty, class Alloc>
        bool operator<(
            const vector<Ty, Alloc>& left,
            const vector<Ty, Alloc>& right);
    template<class Ty, class Alloc>
        bool operator>(
            const vector<Ty, Alloc>& left,
            const vector<Ty, Alloc>& right);
    template<class Ty, class Alloc>
        bool operator<=(
            const vector<Ty, Alloc>& left,
            const vector<Ty, Alloc>& right);
    template<class Ty, class Alloc>
        bool operator>=(
            const vector<Ty, Alloc>& left,
            const vector<Ty, Alloc>& right);
    template<class Ty, class Alloc>
        void swap(
            vector<Ty, Alloc>& left,
            vector<Ty, Alloc>& right);
    }  // namespace stdCopy to clipboard

## `operator!=`

    template<class Ty, class Alloc>
        bool operator!=(
            const vector <Ty, Alloc>& left,
            const vector <Ty, Alloc>& right);Copy to clipboard

The template function returns `!(left == right)`.

## `operator==`

    template<class Ty, class Alloc>
        bool operator==(
            const vector <Ty, Alloc>& left,
            const vector <Ty, Alloc>& right);Copy to clipboard

The template function overloads `operator==` to compare
two objects of template class
[`vector`](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_vector.html#vector). The function returns
`left.size() == right.size() &&
equal(left.
begin(), left.
end(), right.begin())`.

## `operator<`

    template<class Ty, class Alloc>
        bool operator<(
            const vector <Ty, Alloc>& left,
            const vector <Ty, Alloc>& right);Copy to clipboard

The template function overloads `operator<` to compare
two objects of template class
[`vector`](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_vector.html#vector). The function returns
`lexicographical_compare(left.
begin(), left.
end(), right.begin(), right.end())`.

## `operator<=`

    template<class Ty, class Alloc>
        bool operator<=(
            const vector <Ty, Alloc>& left,
            const vector <Ty, Alloc>& right);Copy to clipboard

The template function returns `!(right < left)`.

## `operator>`

    template<class Ty, class Alloc>
        bool operator>(
            const vector <Ty, Alloc>& left,
            const vector <Ty, Alloc>& right);Copy to clipboard

The template function returns `right < left`.

## `operator>=`

    template<class Ty, class Alloc>
        bool operator>=(
            const vector <Ty, Alloc>& left,
            const vector <Ty, Alloc>& right);Copy to clipboard

The template function returns `!(left < right)`.

## `swap`

    template<class Ty, class Alloc>
        void swap(
            vector <Ty, Alloc>& left,
            vector <Ty, Alloc>& right);Copy to clipboard

The template function executes
`left.swap(right)`.

## `vector`

* * *

**`allocator_type· assign· at· back· begin· capacity· clear· const_iterator· const_pointer· const_reference· const_reverse_iterator· difference_type· empty· end· erase· front· get_allocator· insert· iterator· max_size· operator[]· pointer· pop_back· push_back· rbegin· reference· rend· reserve· resize· reverse_iterator· size· size_type· swap· value_type· vector`**

* * *

    template<class Ty, class Alloc = allocator<Ty> >
        class vector {
    public:
        typedef Alloc allocator_type;
        typedef typename Alloc::pointer pointer;
        typedef typename Alloc::const_pointer
            const_pointer;
        typedef typename Alloc::reference reference;
        typedef typename Alloc::const_reference
            const_reference;
        typedef typename Alloc::value_type value_type;
    
        typedef T0 iterator;
        typedef T1 const_iterator;
        typedef T2 size_type;
        typedef T3 difference_type;
        typedef reverse_iterator<const_iterator>
            const_reverse_iterator;
        typedef reverse_iterator<iterator>
            reverse_iterator;
    
        vector();
        explicit vector(const Alloc& al);
        explicit vector(size_type count);
        vector(size_type count, const Ty& val);
        vector(size_type count, const Ty& val,
            const Alloc& al);
        vector(const vector& right);
        template<class InIt>
            vector(InIt first, InIt last);
        template<class InIt>
            vector(InIt first, InIt last,
                const Alloc& al);
    
        iterator begin();
        const_iterator begin() const;
        iterator end();
        const_iterator end() const;
        reverse_iterator rbegin();
        const_reverse_iterator rbegin() const;
        reverse_iterator rend();
        const_reverse_iterator rend() const;
    
        void reserve(size_type count);
        size_type capacity() const;
        void resize(size_type newsize);
        void resize(size_type newsize, Ty val);
        size_type size() const;
        size_type max_size() const;
        bool empty() const;
    
        Alloc get_allocator() const;
    
        reference at(size_type off);
        const_reference at(size_type off) const;
        reference operator[](size_type off);
        const_reference operator[](size_type off) const;
        reference front();
        const_reference front() const;
        reference back();
        const_reference back() const;
    
        void push_back(const Ty& val);
        void pop_back();
    
        template<class InIt>
            void assign(InIt first, InIt last);
        void assign(size_type count, const Ty& val);
    
        iterator insert(iterator where, const Ty& val);
        void insert(iterator where, size_type count, const Ty& val);
        template<class InIt>
            void insert(iterator where, InIt first, InIt last);
    
        iterator erase(iterator where);
        iterator erase(iterator first, iterator last);
        void clear();
    
        void swap(vector& right);
        };Copy to clipboard

The template class describes an object that controls a
varying-length sequence of elements of type `Ty`.
The sequence is stored as an array of `Ty`.

The object allocates and frees storage for the sequence it controls
through a stored [allocator object](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_memory.html#allocator%20object)
of class `Alloc`. Such an allocator object must have
the same external interface as an object of template class
[`allocator`](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_memory.html#allocator).
Note that the stored allocator object is *not* copied when the container
object is assigned.

**Vector reallocation**
occurs when a member function must grow the controlled sequence
beyond its current storage [capacity](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_vector.html#vector::capacity).
Other insertions and erasures may alter various storage addresses
within the sequence. In all such cases,
iterators or references that point at
altered portions of the controlled sequence become
**invalid**.

### `vector::allocator_type`

    typedef Alloc allocator_type;Copy to clipboard

The type is a synonym for the template parameter `Alloc`.

### `vector::assign`

    template<class InIt>
        void assign(InIt first, InIt last);
    void assign(size_type count, const Ty& val);Copy to clipboard

If `InIt` is an integer type, the first member
function behaves the same as `assign((size_type)first, (Ty)last)`.
Otherwise, the
first member function replaces the sequence
controlled by `*this` with the sequence
`[first, last)`, which must *not* overlap
the initial controlled sequence.
The second member function replaces the sequence
controlled by `*this` with a repetition of `count`
elements of value `val`.

### `vector::at`

    const_reference at(size_type off) const;
    reference at(size_type off);Copy to clipboard

The member function returns a reference to the element of the
controlled sequence at position `off`. If that position is
invalid, the function throws an object of class
`out_of_range`.

### `vector::back`

    reference back();
    const_reference back() const;Copy to clipboard

The member function returns a reference to the last element of the
controlled sequence, which must be non-empty.

### `vector::begin`

    const_iterator begin() const;
    iterator begin();Copy to clipboard

The member function returns a random-access iterator that points at
the first element of the sequence (or just beyond the end of an empty
sequence).

### `vector::capacity`

    size_type capacity() const;Copy to clipboard

The member function returns the storage currently allocated to hold
the controlled sequence, a value at least as large as
`size()`.

### `vector::clear`

    void clear();Copy to clipboard

The member function calls
`erase(
begin(),
end())`.

### `vector::const_iterator`

    typedef T1 const_iterator;Copy to clipboard

The type describes an object that can serve as a constant
random-access iterator for the controlled sequence.
It is described here as a
synonym for the implementation-defined type `T1`.

### `vector::const_pointer`

    typedef typename Alloc::const_pointer
        const_pointer;Copy to clipboard

The type describes an object that can serve as a constant pointer
to an element of the controlled sequence.

### `vector::const_reference`

    typedef typename Alloc::const_reference
        const_reference;Copy to clipboard

The type describes an object that can serve as a constant reference
to an element of the controlled sequence.

### `vector::const_reverse_iterator`

    typedef reverse_iterator<const_iterator>
        const_reverse_iterator;Copy to clipboard

The type describes an object that can serve as a constant reverse
iterator for the controlled sequence.

### `vector::difference_type`

    typedef T3 difference_type;Copy to clipboard

The signed integer type describes an object that can represent the
difference between the addresses of any two elements in the controlled
sequence. It is described here as a
synonym for the implementation-defined type `T3`.

### `vector::empty`

    bool empty() const;Copy to clipboard

The member function returns true for an empty controlled sequence.

### `vector::end`

    const_iterator end() const;
    iterator end();Copy to clipboard

The member function returns a random-access iterator that points
just beyond the end of the sequence.

### `vector::erase`

    iterator erase(iterator where);
    iterator erase(iterator first, iterator last);Copy to clipboard

The first member function removes the element of the controlled
sequence pointed to by `where`. The second member function
removes the elements of the controlled sequence
in the range `[first, last)`.
Both return an iterator that designates the first element remaining
beyond any elements removed, or
`end()` if no such element exists.

Erasing `N` elements causes `N` destructor calls
and an assignment for each of the elements between the insertion
point and the end of the sequence. No
[reallocation](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_vector.html#vector%20reallocation) occurs,
so iterators and references become
[invalid](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_vector.html#invalid%20vector%20iterators) only from the first element
erased through the end of the sequence.

The member functions throw an exception only if a copy operation
throws an exception.

### `vector::front`

    reference front();
    const_reference front() const;Copy to clipboard

The member function returns a reference to the first element of the
controlled sequence, which must be non-empty.

### `vector::get_allocator`

    Alloc get_allocator() const;Copy to clipboard

The member function returns the stored
[allocator object](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_memory.html#allocator%20object).

### `vector::insert`

    iterator insert(iterator where, const Ty& val);
    void insert(iterator where, size_type count, const Ty& val);
    template<class InIt>
        void insert(iterator where, InIt first, InIt last);Copy to clipboard

Each of the member functions inserts, before the element pointed to
by `where` in the controlled sequence, a sequence
specified by the remaining operands. The first member function inserts
a single element with value `val` and returns an iterator
that designates the newly inserted element. The second member function
inserts a repetition of `count` elements of value `val`.

If `InIt` is an integer type, the last member
function behaves the same as `insert(where, (size_type)first, (Ty)last)`.
Otherwise, the
last member function inserts the sequence
`[first, last)`, which must *not* overlap
the initial controlled sequence.

When inserting a single element, the number of
element copies is linear in the number of elements between the insertion
point and the end of the sequence. When inserting a single element
at the end of the sequence, the amortized number of element copies
is constant. When inserting `N` elements,
the number of element copies
is linear in `N` plus the number of elements
between the insertion point and the end of the sequence
-- except when the template member
is specialized for `InIt` an input iterator, which
behaves like `N` single insertions.

If
[reallocation](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_vector.html#vector%20reallocation) occurs, the capacity
increases by a fixed factor (at least),
and all iterators and references become
[invalid](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_vector.html#invalid%20vector%20iterators).
If no reallocation occurs, iterators become invalid
only from the point of insertion through the end of the sequence.

If an exception is thrown during the
insertion of one or more elements, and the exception is not thrown while
copying an element, the container is left unaltered
and the exception is rethrown.

### `vector::iterator`

    typedef T0 iterator;Copy to clipboard

The type describes an object that can serve as a random-access
iterator for the controlled sequence.
It is described here as a
synonym for the implementation-defined type `T0`.

### `vector::max_size`

    size_type max_size() const;Copy to clipboard

The member function returns the length of the longest sequence that
the object can control.

### `vector::operator[]`

    const_reference operator[](size_type off) const;
    reference operator[](size_type off);Copy to clipboard

The member function returns a reference to the element of the
controlled sequence at position `off`. If that position is
invalid, the behavior is undefined.

### `vector::pointer`

    typedef typename Alloc::pointer pointer;Copy to clipboard

The type describes an object that can serve as a pointer to an
element of the controlled sequence.

### `vector::pop_back`

    void pop_back();Copy to clipboard

The member function removes the last element of the
controlled sequence, which must be non-empty.

The member function never throws an exception.

### `vector::push_back`

    void push_back(const Ty& val);Copy to clipboard

The member function inserts an element with value `val`
at the end of the controlled sequence.

If an exception is thrown, the container is left unaltered
and the exception is rethrown.

### `vector::rbegin`

    const_reverse_iterator rbegin() const;
    reverse_iterator rbegin();Copy to clipboard

The member function returns a reverse iterator that points just
beyond the end of the controlled sequence. Hence, it designates the
beginning of the reverse sequence.

### `vector::reference`

    typedef typename Alloc::reference reference;Copy to clipboard

The type describes an object that can serve as a reference to an
element of the controlled sequence.

### `vector::rend`

    const_reverse_iterator rend() const;
    reverse_iterator rend();Copy to clipboard

The member function returns a reverse iterator that points at the
first element of the sequence (or just beyond the end of an empty
sequence). Hence, it designates the end of the reverse sequence.

### `vector::reserve`

    void reserve(size_type count);Copy to clipboard

If `count` is greater than
`max_size()`,
the member function reports a
**length error** by
throwing an object of class `length_error`.
Otherwise, it ensures that
`capacity()`
henceforth returns at least `count`.

### `vector::resize`

    void resize(size_type newsize);
    void resize(size_type newsize, Ty val);Copy to clipboard

The member functions both ensure that
`size()` henceforth
returns `newsize`. If it must make the controlled sequence longer,
the first member function appends elements with value `Ty()`,
while the second member function appends elements with value `val`.
To make the controlled sequence shorter, both member functions call
`erase(begin() + newsize, end())`.

### `vector::reverse_iterator`

    typedef reverse_iterator<iterator>
        reverse_iterator;Copy to clipboard

The type describes an object that can serve as a reverse iterator
for the controlled sequence.

### `vector::size`

    size_type size() const;Copy to clipboard

The member function returns the length of the controlled sequence.

### `vector::size_type`

    typedef T2 size_type;Copy to clipboard

The unsigned integer type describes an object that can represent the
length of any controlled sequence. It is described here as a
synonym for the implementation-defined type `T2`.

### `vector::swap`

    void swap(vector& right);Copy to clipboard

The member function swaps the controlled sequences between
`*this` and `right`. If
`get_allocator()
== right.get_allocator()`, it does so in constant time,
it throws no exceptions, and it invalidates no references, pointers,
or iterators that designate elements in the two controlled sequences.
Otherwise, it performs a number of element assignments and constructor calls
proportional to the number of elements in the two controlled sequences.

### `vector::value_type`

    typedef typename Alloc::value_type value_type;Copy to clipboard

The type is a synonym for the template parameter `Ty`.

### `vector::vector`

    vector();
    explicit vector(const Alloc& al);
    explicit vector(size_type count);
    vector(size_type count, const Ty& val);
    vector(size_type count, const Ty& val, const Alloc& al);
    vector(const vector& right);
    template<class InIt>
        vector(InIt first, InIt last);
    template<class InIt>
        vector(InIt first, InIt last, const Alloc& al);Copy to clipboard

All constructors store an
[allocator object](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_memory.html#allocator%20object) and
initialize the controlled sequence. The allocator object is the argument
`al`, if present. For the copy constructor, it is
`right.get_allocator()`.
Otherwise, it is `Alloc()`.

The first two constructors specify an
empty initial controlled sequence. The third constructor specifies
a repetition of `count` elements of value `Ty()`.
The fourth and fifth constructors specify
a repetition of `count` elements of value `val`.
The sixth constructor specifies a copy of the sequence controlled by
`right`.
If `InIt` is an integer type, the last two constructors
specify a repetition of `(size_type)first` elements of value
`(Ty)last`. Otherwise, the
last two constructors specify the sequence
`[first, last)`.

## `vector<bool,
Alloc>`

    template<class Alloc>
        class vector<bool, Alloc> {
    public:
        typedef T4 pointer;
        typedef T5 const_pointer;
        class reference;
        typedef bool const_reference;
    
        typedef T0 iterator;
        typedef T1 const_iterator;
    
        void flip();
        static void swap(reference left, reference right);
    // rest same as template class vector
        };Copy to clipboard

The class is a partial specialization of template class
`vector` for elements of type
`bool`. It alters the definition of four member
types (to optimize the packing and unpacking of elements)
and adds two member functions. Its behavior is otherwise
the same as for template class `vector`.

### `vector<bool,
Alloc>::const_iterator`

    typedef T1 const_iterator;Copy to clipboard

The type describes an object that can serve as a constant
random-access iterator for the controlled sequence.
It is described here as a
synonym for the unspecified type `T1`.

### `vector<bool,
Alloc>::const_pointer`

    typedef T5 const_pointer;Copy to clipboard

The type describes an object that can serve as a pointer
to a constant element of the controlled sequence. It is described here as a
synonym for the unspecified type `T5`.

### `vector<bool,
Alloc>::const_reference`

    typedef bool const_reference;Copy to clipboard

The type describes an object that can serve as a constant reference
to an element of the controlled sequence, in this case `bool`.

### `vector<bool,
Alloc>::flip`

    void flip();Copy to clipboard

The member function inverts the values of all the members of the
controlled sequence.

### `vector<bool,
Alloc>::iterator`

    typedef T0 iterator;Copy to clipboard

The type describes an object that can serve as a random-access
iterator for the controlled sequence. It is described here as a
synonym for the unspecified type `T0`.

### `vector<bool,
Alloc>::pointer`

    typedef T4 pointer;Copy to clipboard

The type describes an object that can serve as a pointer
to an element of the controlled sequence. It is described here as a
synonym for the unspecified type `T4`.

### `vector<bool,
Alloc>::reference`

    class reference {
    public:
        reference& operator=(const reference& right);
        reference& operator=(bool val);
        void flip();
        bool operator~() const;
        operator bool() const;
        };Copy to clipboard

The type describes an object that can serve as a reference to an
element of the controlled sequence. Specifically, for two objects
`ref` and `ref2` of class `reference`:

- **`bool(ref)`** yields the value of the element
designated by `ref`
- **`~ref`** yields the inverted value of the element
designated by `ref`
- **`ref.flip()`** inverts the value designated by `ref`
- **`ref2 = bool(ref)`** and **`ref2 = ref`**
both assign the value of the element
designated by `ref` to the element designated by `ref2`

It is unspecified how member functions of class
`vector<bool>` construct objects of
class `reference` that designate elements of a controlled
sequence. The default constructor for class `reference`
generates an object that refers to no such element.

### `vector<bool,
Alloc>::swap`

    void swap(reference left, reference right);Copy to clipboard

The static member function swaps the members of the
controlled sequences designated by `left` and `right`.

* * *

See also the
**[Table of Contents](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_index.html#Table%20of%20Contents)** and the
**[Index](https://docs.qualcomm.com/doc/80-N3040-23/topic/_cpp_index.html)**.

*[Copyright](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_crit_pjp.html) © 1992-2006by P.J. Plauger. Portions derived from work[copyright](https://docs.qualcomm.com/doc/80-N3040-23/topic/cpp_crit_hp.html) © 1994by Hewlett-Packard Company. All rights reserved.*

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Last Published: Oct 06, 2026

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