std::inserter

Defined in header <iterator>

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)

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 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.

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 <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';
}

Output:

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

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

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`

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

Docs

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