Question

I have an AdjacencyList class and I want all graph algorithms to be seperated from it. Let’s say all algorithms are functors and derive from GraphAlgorithm abstract base class. How do I make it work?

I am currently thinking,

class AdjacencyList
{
    // ...
    friend class GraphAlgorithm;
    // ...
};

But is it allowing GraphAlgorithm’s sub-classes to access private members of AdjacencyList?

Any other approaches are welcome.

Answer 1

But is it allowing GraphAlgorithm’s sub-classes to access private members of AdjacencyList?

No, it does not. Friendship is not transitive.

Regardless, whenever you need a friend declaration, you should regard it as a code smell and re-think your design.

I would rather have getters in the AdjacencyList and so a GraphAlgorithm can operate on the members it has access to from the methods of AdjacencyList.