List Iterator Implementation Lecture 33 Fri, Apr 13, 2007

List Traversals To traverse a list is to move from one end to the other, “visiting” each node along the way. Forward traversals go from head to tail Reverse traversals go from tail to head. The meaning of “visiting” a node is left unspecified at this point. The meaning will be specified at the time of the traversal. 5/3/2019 List Iterators

The Traversal Function Introduce a new List member function The parameter, named visit, is a pointer to a function. The function visit() has prototype void traverse(ListIterator& it, void (* visit)(ListIterator&)); void visit(ListIterator&); 5/3/2019 List Iterators

Traversals and Iterators A traversal may be implemented as follows. void traverse(ListIterator& it, void (* visit)(ListIterator&)) { for (it.begin(); !it.atEnd(); ++it) visit(it); return; } 5/3/2019 List Iterators

Example: Print the List Define a visiting function print(). Use print() to print (visit) the members of the List. void print(ListIterator& it) { cout << *it << endl; return; } ListIterator it(list); list.traverse(it, print); 5/3/2019 List Iterators

The Visiting Function Suppose we made print() a member function. The program would not compile because the prototype of print() would be What can be done about this? void print(List* this, ListIterator& it); 5/3/2019 List Iterators

Static Member Functions A static member function does not have the implicit this parameter. It may not invoke any non-static member function. If we make print() a static member function then it will work. static void print(ListIterator& it); 5/3/2019 List Iterators

Implemention of Reverse Iterators To construct a reverse iterator for a linked list, Push NULL onto the stack. Then push the addresses of the nodes onto a stack. To increment the reverse list iterator Pop an address off the stack. Assign it to the node pointer. 5/3/2019 List Iterators

Insertion Sort with Iterators InsertionSortwIter.cpp 5/3/2019 List Iterators