std::inserter

From cppreference.com
< cpplrm; | iterator
Defined in header <iterator>
template< class Container >
std::insert_iterator<Container> inserter( Container& c, typename Container::iterator i );

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.

Parameters

c - container that supports a 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.

Possible implementation

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

Example

#include <algorithm>
#include <iostream>
#include <iterator>
#include <vector>
#include <set>

int main()
{

    std::multiset<int> s {1, 2, 3};

    // std::inserter is commonly used with 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> l {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(l, std::next(l.begin())));

    for (int n : l)
        std::cout << n << ' ';
    std::cout << '\n';
}

Output:

1 2 2 2 2 2 2 3 
1 100 200 300 2 3 4 5

See also

iterator adaptor for insertion into a container
(class template)
creates a std::back_insert_iterator of type inferred from the argument
(function template)
creates a std::front_insert_iterator of type inferred from the argument
(function template)