general purpose Singly-linked list implementation with inheritance

[andrey_zh]

The challenge is to implement a general purpose Singly-linked list.

I've found a good decision with templates, it looks natural and works good, but it's too long to write something like list->get_node()->get_data()->get_some_stuff()->set_value(value), when number of fields is more than one, and I have to add class or structure to a node. So class template is not the thing i'm searching for.

Particularly, I want to incorporate new fields to a node witch is an inner class of a Slist class.
But I'm stuck with syntax

Here is my code:


class Slist
{
private:
class Node; // just enough for a node
class Sentinel; // sentinel node, no data fields

protected:
class Data; // data node, opened for inheritance - ???

private:
Sentinel *first_node;
Node *last_node;
};



class Slist::Node
{
public:
// trivial interface stuff
private:
Node *next_node;
};

class Slist::Sentinel : public Slist::Node
{
// it seems, that's all
};

class Slist:ata : public Slist::Node
{
// that's all, but only for some time
};

That is to say, I want to inherit Slist and add fields to it's inner class Data
How it could be done?

P.S.: What will happen in such an erroneous case:
((Node *)(first_node/*Remenber, It's Sentinel*/))->call_some_interface_method_of_Data_class()
?