std::vector<T,Allocator>::assign

 

C++

Compiler support

Freestanding and hosted

Language

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical specifications

Symbols index

External libraries

 

Containers library

Sequence

array (C++11)

vector

deque

forward_list (C++11)

list

Associative

set

multiset

map

multimap

Unordered associative

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

Adaptors

stack

queue

priority_queue

Views

span (C++20)

 

std::vector

Member functions

vector::vector

vector::~vector

vector::operator=

vector::assign

vector::get_allocator

Element access

vector::at

vector::operator[]

vector::front

vector::back

vector::data

Iterators

vector::beginvector::cbegin (C++11)

vector::endvector::cend (C++11)

vector::rbeginvector::crbegin (C++11)

vector::rendvector::crend (C++11)

Capacity

vector::empty

vector::size

vector::max_size

vector::reserve

vector::capacity

vector::shrink_to_fit (C++11)

Modifiers

vector::clear

vector::insert

vector::emplace (C++11)

vector::erase

vector::push_back

vector::emplace_back (C++11)

vector::pop_back

vector::resize

vector::swap

Non-member functions

std::swap

eraseerase_if (C++20)(C++20)

operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)

Deduction guides(C++17)

 

	(1)
void assign( size_type count, const T& value );			(until C++20)
constexpr void assign( size_type count, const T& value );			(since C++20)
		(2)
template< class InputIt > void assign( InputIt first, InputIt last );				(until C++20)
template< class InputIt > constexpr void assign( InputIt first, InputIt last );				(since C++20)
			(3)
void assign( std::initializer_list<T> ilist );					(since C++11) (until C++20)
constexpr void assign( std::initializer_list<T> ilist );					(since C++20)

Replaces the contents of the container.

1) Replaces the contents with count copies of value value

2) Replaces the contents with copies of those in the range [first, last). The behavior is undefined if either argument is an iterator into *this.

This overload has the same effect as overload (1) if InputIt is an integral type.	(until C++11)
This overload participates in overload resolution only if InputIt satisfies LegacyInputIterator.	(since C++11)

3) Replaces the contents with the elements from the initializer list ilist.

All iterators, pointers and references to the elements of the container are invalidated. The past-the-end iterator is also invalidated.

Parameters

count	-	the new size of the container
value	-	the value to initialize elements of the container with
first, last	-	the range to copy the elements from
ilist	-	initializer list to copy the values from

Complexity

1) Linear in count

2) Linear in distance between first and last

3) Linear in ilist.size()

Example

The following code uses assign to add several characters to a std::vector<char>:

Run this code

#include <vector>
#include <iostream>
#include <string>
 
int main()
{
    std::vector<char> characters;
 
    auto print_vector = [&](){
        for (char c : characters)
            std::cout << c << ' ';
        std::cout << '\n';  
    };
 
    characters.assign(5, 'a');
    print_vector();
 
    const std::string extra(6, 'b');
    characters.assign(extra.begin(), extra.end());
    print_vector();
 
    characters.assign({'C', '+', '+', '1', '1'});
    print_vector();
}

Output:

a a a a a 
b b b b b b 
C + + 1 1

See also

(constructor)

constructs the vector (public member function)