C++ In a Nutshell

Name

front_insert_iterator class template — Iterator to insert elements at the front of a container

Synopsis

template <typename 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);
  front_insert_iterator<Container>&
    operator=(typename Container::const_reference value);
  front_insert_iterator<Container>& operator*(  );
  front_insert_iterator<Container>& operator++(  );
  front_insert_iterator<Container> operator++(int);
};

The front_insert_iterator class template implements an output iterator that stores elements in a container by calling the container’s push_front function. The most convenient way to create a front_insert_iterator object is to use the front_inserter function template.

The way front_insert_iterator works seems slightly unconventional, although it is perfectly reasonable for an output iterator: the * operator returns the iterator, not an element of the container. Thus, the expression *iter = value assigns value to the iterator itself. The iterator’s assignment operator adds value to the underlying container by calling the container’s push_front function. Thus, the iterator does not maintain any notion of a position, and the increment operator is a no-op.

The following are the member functions of front_insert_iterator:

explicit front_insert_iterator (Container& x)

Initializes the container member with &x.

front_insert_iterator<Container>& ...