Hello. I'm new to c++ and I am trying to program a graph class template with unspecified vertex and edge objects. My problem is, how do I reference a type which is defined inside the template class outside of its definition? The problem is illustrated in the following piece of code.

template <class TV, class TE>
class graph
{
public:

	class vertex;				// forward declaration of a vertex

	typedef vertex * VPtr;			// a pointer to a vertex

	typedef map<VPtr,TE> Eset;		// a set of edges; 
						// VPtr points to a target vertex 
						// and TE is some edge data (e.g capacity)

	class vertex : public TV		// endows a custom vertex of type TV 
						// with a set of neighbors nn
	{
		Eset nn;
	};

	typedef list<vertex> Vlist;		// a list of vertices

	VPtr choose_random_vertex();		// chooses vertex randomly

private :
	Vlist V;
};

template <class TV, class TE>
VPtr graph<TV,TE>::choose_random_vertex()  // error : expected constructor, destructor,
					   // or type conversion before 'graph'
{
	// choose vertex randomly
}

Obviously the implementation of the function choose_random_vertex() does not compile because VPtr is not known. It would work if I gave an inline definition of the function inside the graph template, but this I don't want.

It is most definitely an issue of programming style. Which is what I have no experience with in c++. Hints and nudges are highly appreciated.