std::front_insert_iterator (3) Linux Manual Page

std::front_insert_iterator – std::front_insert_iterator

Synopsis

Defined in header<iterator>

    template <class Container>

    class front_insert_iterator : public std::iterator<std::output_iterator_tag, (until C++ 17)

                                                                                     void,
                                                       void, void, void>

                                  template <class Container>
                                  (since C++ 17)

                                      class front_insert_iterator;

std::front_insert_iterator is an LegacyOutputIterator 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

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

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

These member types are required to be obtained by inheriting from std::iterator<std::output_iterator_tag, void, void, void, void>. (until C++17)

Example

// Run this code

#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:

  5 4 3 2 1

See also

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