std::front_insert_iterator

Defined in header <iterator>

template< class Container >
class front_insert_iterator : public std::iterator< std::output_iterator_tag,
                                                   void,void,void,void >

(until C++17)

template< class Container >
class front_insert_iterator;

(since C++17)

std::front_insert_iterator is an OutputIterator that prepends elements to a container for which it was constructed. The container's push_front() member function is called whenever the iterator (whether dereferenced or not) is assigned to. Incrementing the std::front_insert_iterator is a no-op.

Member types

Member type	Definition
`container_type`	`Container`

Member functions

(constructor)	constructs a new `front_insert_iterator` (public member function)
operator=	inserts an object into the associated container (public member function)
operator*	no-op (public member function)
operator++operator++(int)	no-op (public member function)

Member objects

Member name	Definition
`container` (protected)	a pointer of type `Container*`

Member types

Member type	Definition
`value_type`	`void`
`difference_type`	`void`
`pointer`	`void`
`reference`	`void`
`iterator_category`	`std::output_iterator_tag`

Note: before C++17, these member types are required to be obtained by inheriting from std::iterator<std::output_iterator_tag,void,void,void,void>.

Example

#include <vector>
#include <deque>
#include <iostream>
#include <iterator>
#include <algorithm>
int main()
{
    std::vector<int> v{1,2,3,4,5};
    std::deque<int> d;
    std::copy(v.begin(), v.end(),
              std::front_insert_iterator<std::deque<int>>(d)); // or std::front_inserter(d)
    for(int n : d)
        std::cout << n << ' ';
    std::cout << '\n';
}

Output:

1	`5 4 3 2 1`

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

std::front_insert_iterator

Member types

Member functions

Member objects

Member types

Example

See also