STL sets have the following operations: s.begin(); s.end() // an iterator pointing to the first element // one past the last element

Iterators are a generalization of pointers in C++ and have similar semantics. They allow a program to navigate through di erent types of containers in a uniform manner.

Using an iterator, we don’t need to know how the collection is implemented!

Use an iterator An object containing an internal state variable (i.e. a pointer or index) that moves one step in the list at a time as you iterate, saving your position

Iterators are objects that provide access to the elements in a collection.

We want the code using iteration to be independent of the type of aggregate being used. Who controls iteration? Who defines the traversal algorithm? How robust is the iterator? STL <vector>, <list>, …

STL Input Iterator Example int main () { // An initially empty vector.