back_insert_iterator - C++ Reference

back_insert_iterator

class template

template <class Container> class back_insert_iterator;

<iterator>

Back insert iterator

Back insert iterators are a special output iterator class designed to allow algorithms that usually overwrite elements (such as copy) to instead insert new elements at the end of the container.

The container must have member push_back defined (such as standard containers vector, deque and list).

Using the assignment operator on the back_insert_iterator, even when dereferenced, causes the container to append a new element to it. The other typical operators of an output iterator are also defined for back_insert_iterator but have no effect.

It is defined with an identical operation to:

template <class Container>
  class back_insert_iterator :
    public iterator<output_iterator_tag,void,void,void,void,void>
{
protected:
  Container* container;

public:
  typedef Container container_type;
  explicit back_insert_iterator (Container& x) : container(x) {}
  back_insert_iterator<Container>& operator= (typename Conatiner::const_reference value)
    { container->push_back(value); return *this; }
  back_insert_iterator<Container>& operator* ()
    { return *this; }
  back_insert_iterator<Container>& operator++ ()
    { return *this; }
  back_insert_iterator<Container> operator++ (int)
    { return *this; }
};

The library provides a function, called back_inserter, that automatically generates a back_insert_iterator class from a container.

Member functions

constructor: back_insert_iterator objects are constructed from a container.
operator=: Inserts a new element in the container, initializing its value to a copy of the argument.
operator*: Does nothing. Returns a reference to the object.
operator++: Does nothing. Returns a reference to the object.

Example

// back_insert_iterator example
#include <iostream>
#include <iterator>
#include <vector>
using namespace std;

int main () {
  vector<int> firstvector, secondvector;
  for (int i=1; i<=5; i++)
  { firstvector.push_back(i); secondvector.push_back(i*10); }

  back_insert_iterator< vector<int> > back_it (firstvector);

  copy (secondvector.begin(),secondvector.end(),back_it);

  vector<int>::iterator it;
  for ( it = firstvector.begin(); it!= firstvector.end(); ++it )
	  cout << *it << " ";
  cout << endl;

  return 0;
}

Output:


1 2 3 4 5 10 20 30 40 50


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Member functions

Example

See also