back_insert_iterator, back_inserter

Insert Iterator

• Summary
• Data Type and Member Function Indexes
• Synopsis
• Description
• Interface
• Constructor
• Operators
• Helper Function
• Example
• Warning
• See Also

An insert iterator used to insert items at the end of a collection.

Member Functions

back_inserter() operator*() operator++() operator=()

#include <iterator>

template <class Container> 
class back_insert_iterator : public output_iterator;

Insert iterators let you insert new elements into a collection rather than copy a new element's value over the value of an existing element. The class back_insert_iterator is used to insert items at the end of a collection. The function back_inserter creates an instance of a back_insert_iterator for a particular collection type. A back_insert_iterator can be used with vectors, deques, and lists, but not with maps or sets.

template <class Container>
 class back_insert_iterator : public output_iterator {

protected:
   Container& container;
public:
   back_insert_iterator (Container&);
   back_insert_iterator<Container>&
    operator= (const Container::value_type&);
   back_insert_iterator<Container>& operator* ();
   back_insert_iterator<Container>& operator++ ();
   back_insert_iterator<Container> operator++ (int);
};

template <class Container>
 back_insert_iterator<Container> back_inserter (Container&);

back_insert_iterator (Container& x);

Constructor. Creates an instance of a back_insert_iterator associated with container x.

back_insert_iterator<Container>&
operator= (const Container::value_type& value);

Inserts a copy of value on the end of the container, and returns *this.

back_insert_iterator<Container>& 
operator* ();

Returns *this.

back_insert_iterator<Container>& 
operator++ ();
back_insert_iterator<Container> 
operator++ (int);

Increments the input iterator and returns *this.

template <class Container>
back_insert_iterator<Container>
back_inserter (Container& x)

Returns a back_insert_iterator that will insert elements at the end of container x. This function allows you to create insert iterators inline.

//
// ins_itr.cpp
//
 #include <iterator>
 #include <deque>
 #include <iostream.h>

 int main ()
 {
   //
   // Initialize a deque using an array.
   //
   int arr[4] = { 3,4,7,8 };
   deque<int> d(arr+0, arr+4);
   //
   // Output the original deque.
   //
   cout << "Start with a deque: " << endl << "     ";
   copy(d.begin(), d.end(),
        ostream_iterator<int,char>(cout," "));
   //
   // Insert into the middle.
   //
   insert_iterator<deque<int> > ins(d, d.begin()+2);
   *ins = 5; *ins = 6;
   //
   // Output the new deque.
   //
   cout << endl << endl;
   cout << "Use an insert_iterator: " << endl << "     ";
   copy(d.begin(), d.end(),
        ostream_iterator<int,char>(cout," "));
   //
   // A deque of four 1s.
   //
   deque<int> d2(4, 1);
   //
   // Insert d2 at front of d.
   //
   copy(d2.begin(), d2.end(), front_inserter(d));
   //
   // Output the new deque.
   //
   cout << endl << endl;
   cout << "Use a front_inserter: " << endl << "     ";
   copy(d.begin(), d.end(),
        ostream_iterator<int,char>(cout," "));
   //
   // Insert d2 at back of d.
   //
   copy(d2.begin(), d2.end(), back_inserter(d));
   //
   // Output the new deque.
   //
   cout << endl << endl;
   cout << "Use a back_inserter: " << endl << "     ";
   copy(d.begin(), d.end(),              
        ostream_iterator<int,char>(cout," "));
   cout << endl;

   return 0;
 }

Output :
Start with a deque:
     3 4 7 8
Use an insert_iterator:
     3 4 5 6 7 8
Use a front_inserter:
     1 1 1 1 3 4 5 6 7 8
Use a back_inserter:
     1 1 1 1 3 4 5 6 7 8 1 1 1 1

If your compiler does not support default template parameters then you need to always supply the Allocator template argument. For instance you'll have to write:

vector<int,allocator<int> >

instead of:

vector<int>

Insert Iterators

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