class template
std::front_insert_iterator
<iterator>
template <class Container> class front_insert_iterator;
Front insert iterator
Front 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 front of the container.
The container must have member
push_front defined (such as standard containers
deque and
list).
Using the assignment operator on the
front_insert_iterator, even when dereferenced, causes the container to insert a new element at its beginning. The other typical operators of an
output iterator are also defined for
front_insert_iterator but have no effect.
It is defined with an identical operation to:
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template <class Container>
class front_insert_iterator :
public iterator<output_iterator_tag,void,void,void,void>
{
protected:
Container* container;
public:
typedef Container container_type;
explicit front_insert_iterator (Container& x) : container(&x) {}
front_insert_iterator<Container>& operator= (typename Container::const_reference value)
{ container->push_front(value); return *this; }
front_insert_iterator<Container>& operator* ()
{ return *this; }
front_insert_iterator<Container>& operator++ ()
{ return *this; }
front_insert_iterator<Container> operator++ (int)
{ return *this; }
};
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The library provides a function, called
front_inserter, that automatically generates a
front_insert_iterator class from a container.
Member functions
- constructor
- front_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
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// front_insert_iterator example
#include <iostream>
#include <iterator>
#include <deque>
using namespace std;
int main () {
deque<int> firstdeque, seconddeque;
for (int i=1; i<=5; i++)
{ firstdeque.push_back(i); seconddeque.push_back(i*10); }
front_insert_iterator< deque<int> > front_it (firstdeque);
copy (seconddeque.begin(),seconddeque.end(),front_it);
deque<int>::iterator it;
for ( it = firstdeque.begin(); it!= firstdeque.end(); ++it )
cout << *it << " ";
cout << endl;
return 0;
}
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Output:
See also
- front_inserter
- Constructs a front insert iterator (function template)
- back_insert_iterator
- Back insert iterator (class template
)
- insert_iterator
- Insert iterator (class template)