Note: These function declarations are not exactly as the appear in the STL. I have simplified them for presentation purposes.
bool operator!=(iterator &i);- returns true if the iterator has the same value as iterator i; otherwise returns false.
T &operator*();- returns the element referenced by the iterator.
iterator& operator++(); // prefix increment- returns the iterator after advancing it to the next
element in the deque.iterator operator++(int); // postfix increment- advanced the iterator to the next element in the deque;
returns the value of the iterator prior to incrementing.