# std::inserter

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< cpp‎ | 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)

`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

Run this code

    #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`

### See also

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)

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