I'd like an iterator in C++ that can only iterate over elements of a specific type. In the following example, I want to iterate only on elements that are SubType instances.

```
vector<Type*> the_vector;
the_vector.push_back(new Type(1));
the_vector.push_back(new SubType(2)); //SubType derives from Type
the_vector.push_back(new Type(3));
the_vector.push_back(new SubType(4)); 

vector<Type*>::iterator the_iterator; //***This line needs to change***

the_iterator = the_vector.begin();
while( the_iterator != the_vector.end() ) {
    SubType* item = (SubType*)*the_iterator;
    //only SubType(2) and SubType(4) should be in this loop.
    ++the_iterator;
}

```

How would I create this iterator in C++?