Trouble Setting up Doubly Linked List

[joatmon]

I'm trying to use a class to set up a doubly linked list so that the pointers to the first and last nodes are returned correctly.

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my_DLL("987"); cout << my_DLL.get_first_char();

cout << my_DLL.first_char->data(); <---outputs 0!!!!

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class DLL { public: DLL::DLL( const string &initial_string) { string my_input = init_value; int this_digit; D_Node<string> first_node((my_input[0] - 48), NULL, NULL); D_Node<int> *head_ptr; D_Node<int> *tail_ptr; head_ptr = &first_node; tail_ptr = &first_node; for (size_t i = 1; i < my_input.length(); i++) { this_digit = my_input[i] - 48; dlist_tail_insert(tail_ptr, this_digit); } first_char = head_ptr; last_char = tail_ptr; cout << first_char << endl;

cout << first_char->data() << endl; <---outputs '9' } private: D_Node<int> *first_digit; D_Node<int> *ones_digit; };

The problem is that when all of this finishes, my two pointers don't work. They have the correct memory addresses stored in them, but when I try to use them, they return the wrong data. Can anybody see why this isn't working?

Thanks!

(p.s. sorry about the formatting in this post. Can't figure that out, either. Not my day, I guess.)

[helios]

You're creating your first_node on the stack. Nodes should be created in the heap.

[Zhuge]

The formatting issue is probably having three dashes --- in the code somewhere. I believe that splits it into an output window to the side.

[joatmon]

Thanks. Not exactly sure how to do this. Here is my attempt, but it's not working:

D_Node<int> first_node((my_input[0] - 48), NULL, NULL);

first_node = new D_Node<int>;
first_node->set_data(my_input[0] - 48);
first_node->set_fore(NULL);
first_node->set_back(NULL);

My error is

first_node is not declared in this scope

Dynamic memory is still an Achilles heel for me. I thought that my new line 1 should create this variable. What am I missing?

Thanks.

@Zhuge - thanks for the three-dash information. I was using that to focus on where my issues were surfacing.

[joatmon]

Never mind. I figured it out. I forgot to put a type in front of first_node.

Thanks a lot. I've spent tons of time on this, so it's good to have it figured out.