std::inserter

Since C++20

Header: <iterator>

inserter is a convenience function template that constructs a std::insert_iterator for the container c and its iterator i with the type deduced from the type of the argument.

# Declarations

template< class Container >
std::insert_iterator<Container>
inserter( Container& c, typename Container::iterator i );

(until C++20)

template< class Container >
constexpr std::insert_iterator<Container>
inserter( Container& c, ranges::iterator_t<Container> i );

(since C++20)

# Parameters

c: container that supports an insert operation
i: iterator in c indicating the insertion position

# Return value

A std::insert_iterator which can be used to insert elements into the container c at the position indicated by i.

# Example

#include <algorithm>
#include <iostream>
#include <iterator>
#include <set>
#include <vector>
 
int main()
{
    std::multiset<int> s{1, 2, 3};
 
    // std::inserter is commonly used with multi-sets
    std::fill_n(std::inserter(s, s.end()), 5, 2);
 
    for (int n : s)
        std::cout << n << ' ';
    std::cout << '\n';
 
    std::vector<int> d{100, 200, 300};
    std::vector<int> v{1, 2, 3, 4, 5};
 
    // when inserting in a sequence container, insertion point advances
    // because each std::insert_iterator::operator= updates the target iterator
    std::copy(d.begin(), d.end(), std::inserter(v, std::next(v.begin())));
 
    for (int n : v)
        std::cout << n << ' ';
    std::cout << '\n';
}

# Defect reports

DR	Applied to	Behavior as published	Correct behavior
LWG 561	C++98	the type of i was independent of Container	it is the iterator type of Container