Should this bunch of typedefs be private or public?

Question

I'm writing a class that represents a graph, so I've wrote the following header

class Graph {
public:
  Graph(); 
  Graph(int N);

  void addVertex();
  void addEdge(VertexNum v1, VertexNum v2, Weight w);


  std::pair<PathLength, Path> shortestPath
    (const VerticesGroup& V1, const VerticesGroup& V2);


private:
  typedef int                           VertexNum;
  typedef int                           Weight;
  typedef std::pair<VertexNum, Weight>  Edge;
  typedef std::vector<Edge>             Path;
  typedef size_t                        PathLength;
  typedef std::vector<VertexNum>        VerticesGroup;


  std::vector<std::list<Edge> > adjList;

  bool incorrectVertexNumber(VertexNum v);
};

I have some questions about the above code:

1. Should I declare the bunch of typedefs public or private?
2. Is it a normal practice, when one typedefs one type to different synonyms (like typedef int VertexNum; typedef int Weight;)?

Answer 1

1. Access control in C++ is applied purely to names. There's a note and example in ISO/IEC 14882:2011 11 [class.access]/4 that makes it clear that this is the intention.

[...] [ Note: Because access control applies to names, if access control is applied to a typedef name, only the accessibility of the typedef name itself is considered. The accessibility of the entity referred to by the typedef is not considered. For example,

class A {
  class B { };
public:
  typedef B BB;
};

void f() {
   A::BB x; // OK, typedef name A::BB is public
  A::B y; // access error, A::B is private
}
—end note ]

2. it is ok, as you can make some type meaningful and easily understandable.

Answer 2

Any typedef used in the public interface of the class should be in the public section of the class. Rest should be private.

Answer 3

1. If you declare as private, you will not be able to use them outside your class. I guess this is not what you want, specially if the typedefed name appears as parameter type in your public interface. If you restrict using the typedefed name within your class, then make it private.
2. It is certainly common practice to rename a type using typedef to a more usable/easily understandable name at the domain level.