How avoid code duplication in visitor and const visitor base classes

Question

I have 2 classes ConstVisitorBase and VisitorBase which contain some code to visit objects. for example:

struct Node
{
    enum class Type { ... };
    Type type;
}

class ConstVisitorBase
{
    public:
        virtual void VisitType1( Node const & node );
        ...

    private:
        void VisitNode( Node const & node )
        {
            switch( node.type )
            {
                case Node::Type::type1: VisitType1( node );
            }
            ...
        }
}

class VisitorBase
{
    public:
        virtual void VisitType1( Node & node );
        ...

    private:
        void VisitNode( Node & node )
        {
            switch( node.type )
            {
                case Node::Type::type1: VisitType1( node );
            }
            ...
        }
}

The code for the private method VisitNode is identical other than the const specifier.

Is there a way to avoid this duplication?
Even when there are multiple methods involved ( VisitNode calling EnterNode and LeaveNode )?

Answer 1

Since VisitType1 are public and the two classes are unrelated, you can use a template function:

template<typename Visitor, typename T>
void dispatch_visits(Visitor& visitor, T&& node){
    switch( node.type )
    {
        case Node::Type::type1: visitor.VisitType1( node );
    }
    ...
}