front_insert_iterator<Container>

The front_insert_iterator is an iterator adapter that acts as an output iterator, but which converts expressions of the form *itr = value into calls to push_front on an STL container. The front_insert_iterator constructor takes in a reference to another STL container class that should have push_front invoked on it. Because the front_insert_iterator calls push_front on the element it wraps, the container type must support the push_front function. Consequently, you cannot use a front_insert_iterator on an STL map or set; for those classes, consider using insert_iterator. Also, since vector does not support push_front, you cannot use a front_insert_iterator on an STL vector.

front_insert_iterator is a template type whose argument is the type of container to which the front_insert_iterator should forward its requests. For example, to invoke push_front on a container of type deque<int>, you would use a front_insert_iterator<deque<int> >. Remember to include the extra space between the closing angle brackets or you will get a compile-time error!

Since the above syntax can get a bit clunky, the STL provides a utility function, front_inserter, which creates front_insert_iterators.

front_insert_iterator<Container> Utility Functions

front_insert_iterator<Container> front_inserter(Container &toWrap);

Constructs a front_insert_iterator

copy(v.begin(), v.end(), front_inserter(out)); // Copy from container v into container out

Constructs a new front_insert_iterator that calls push_front on the element specified as the parameter when dereferenced. It is preferable to create front_insert_iterators using front_inserter rather than through a constructor call, since the compiler will figure out the correct type of front_insert_iterator to create. Since in most cases you will create front_insert_iterators as parameters to functions, this function also lets you avoid writing out the type of the front_insert_iterator longhand.

front_insert_iterator<Container> Member Functions

front_insert_iterator<Container>(Container &target)

Constructs a front_insert_iterator on the specified element.

front_insert_iterator<deque<int> > itr(myDeque); // Constructs a front_insert_iterator that pushes elements into myDeque.

Constructs a new front_insert_iterator that calls push_front on the element specified as the parameter when dereferenced.