std::inserter

Defined in header <iterator> 
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)

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)

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