How to define a recursive type?

Question

I want to have a list. An entry in the list would store a value as well as an iterator to another entry in the list. How do I define this type? It\'d be something like this,

Answer 1

Let's turn the problem inside-out with a sprinkle of user-defined types to break the declarations' recursion :

struct Node {
    int _value;
    std::list::const_iterator _next;
};

If you want to use a typedef, well you can :

struct Node;
typedef std::list NodeList;

struct Node {
    int _value;
    NodeList::const_iterator _next;
};

Edit: As T.C. reminded me, instantiating standard containers with incomplete types may be Undefined Behaviour (some standard library implementations do guarantee it's not). So, let's postpone all of it to a later point.

Edit: Well that doesn't help either. So, verify that your std::list implementation supports incomplete types (or trust it to do so, it often works to be honest), or use Boost::containers.

template 
struct Node_ {
    int _value;
    typename std::list::const_iterator _next;
};

typedef Node_<> Node;