Question

Say I have a linked list node class

class node {
    private: 
        node *next_node;
    public:
        node *next() const;
};

node *node::next() const {
    return next_node;
}

Does next() return a node **next_node or node *next_node. Also what is the significance of either in implementing the list class functions (ie. insert, remove, find)?

The reason I would think it returns a **next_node is because next_node is already a pointer and returning it in a function as a pointer would make it a pointer to a pointer. I read in other questions such as: Linked list head double pointer passing that double pointers also work in list operations so I was a bit confused.

Answer 1

The node::next() function as implemented is returning a copy of the next_node member variable. Both next_node and this copy point to the same node instance but they are otherwise independent of each other.

Here is some rather bad ASCII art that tries to demonstrate their relationship

next_node ----> [node instance]
                ^
the copy ------/