A question on vectors, pointers and iterators

Question

Guys, I have a midterm examination tomorrow, and I was looking over the sample paper, and I'm not sure about this question. Any help would be appreciated.

Let v be a vector<Thingie*>, so that each element v[i] contains a pointer to a Thingie. If p is a vector<Thingie*>::iterator, answer the following questions:

1. what type is p?
2. what type is *p?
3. what code provides the address of the actual Thingie?
4. what code provides the actual Thingie?

Answer 1

what type is p?

p is of type vector<Thingie*>::iterator, whatever type that happens to be.

what type is *p?

*p is a Thingie*&; that is, it is a reference to the element in the vector at which the iterator points.

what code provides the address of the actual Thingie?

*p, since the elements of the vector are pointers to the Thingies, and *p gives a reference to the element in the vector.

what code provides the actual Thingie?

**p; that is, you dereference the pointer obtained by *p to obtain the referent of the pointer.

Answer 2

p is vector::iterator

*p is a pointer to a Thingie

v[i]

*v[i]