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POstruct with template object inside an templated class
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copied!<p>I am trying to create a Templated class to hold different objects to lern a bit about selfwritten datastructures and ptrs which are new to me. I am stuck at this point:</p> <pre><code>template <class T> class Linked_List { struct Node { T data; Node* prev; Node* next; Node(T d, Node* p, Node* n) : data(d), prev(p), next(n) {} }; public: Linked_List(); ~Linked_List(); void push_back(T data); void push_front(T data); void insertAt(T data, int pos); T pop_back(); T pop_front(); int size(); bool empty(); private: Node* tail; Node* head; }; </code></pre> <p>I get this error: <code>'Linked_List<T>::Node::data' uses undefined class 'T'</code>. (using VS2013)</p> <p>What have i done wrong? </p> <p>Thanks </p> <hr> <p>Update:</p> <pre><code>#include "Linked_List.h" template<class T> Linked_List<T>::Linked_List() { head = 0; tail = 0; } template<class T> Linked_List<T>::~Linked_List() { { while (head) { Node* temp(head); //pointer to head head = head->next; // go to next delete temp; //delete the pointer } } } template <class T> void Linked_List<T>::push_back(T data) { //create the new Node tail = new Node(data, tail, NULL); if (tail->prev) //add to tail tail->prev->next = tail; if (empty()) // if empty its also the head head = tail; } template <class T> void Linked_List<T>::push_front(T data) { head = new Node(data, 0, tail); if (head->next) head->next->prev = head; if (empty()) tail = head; } template <class T> bool Linked_List<T>::empty() { return (!head || !tail); } template <class T> T Linked_List<T>::pop_back() { if (empty()) throw("Linked_list is empty!"); //pointer to the element we want to have Node* temp(tail); //set the tail to prev tail = tail->prev; //get the data T data = temp->data; //the prev does not have a next now if (tail) tail->next = 0; else head = 0; //delete the node which held our data delete temp; //return the data return data; } template <class T> T Linked_List<T>::pop_front() { if (empty()) throw("Linked_list is empty!"); //pointer to the element we want to have Node* temp(head); //set the tail to prev head = head->next; //get the data T data = temp->data; //the prev does not have a next now if (head) head->prev = 0; else tail = 0; //delete the node which held our data delete temp; //return the data return data; } </code></pre> <p>new stacktrace if i am trying to use it simply like this</p> <pre><code>int main(){ Linked_List<int> list; for (int i = 0; i < 20; i++) { list.push_back(i); } for (int j = 0; j < 20; j++) { cout << list.pop_back() << endl; } } </code></pre> <p>Error:</p> <pre><code> Error 1 error LNK2019: unresolved external symbol "public: __thiscall Linked_List<int>::Linked_List<int>(void)" (??0?$Linked_List@H@@QAE@XZ) referenced in function _main C:\Users\...\Documents\Visual Studio 2013\Projects\Double_Linked_List\Double_Linked_List\main.obj Double_Linked_List Error 2 error LNK2019: unresolved external symbol "public: __thiscall Linked_List<int>::~Linked_List<int>(void)" (??1?$Linked_List@H@@QAE@XZ) referenced in function _main C:\Users\...\Documents\Visual Studio 2013\Projects\Double_Linked_List\Double_Linked_List\main.obj Double_Linked_List Error 3 error LNK2019: unresolved external symbol "public: void __thiscall Linked_List<int>::push_back(int)" (?push_back@?$Linked_List@H@@QAEXH@Z) referenced in function _main C:\Users\...\Documents\Visual Studio 2013\Projects\Double_Linked_List\Double_Linked_List\main.obj Double_Linked_List Error 4 error LNK2019: unresolved external symbol "public: int __thiscall Linked_List<int>::pop_back(void)" (?pop_back@?$Linked_List@H@@QAEHXZ) referenced in function _main C:\Users\...\Documents\Visual Studio 2013\Projects\Double_Linked_List\Double_Linked_List\main.obj Double_Linked_List Error 5 1 error LNK1120: 4 unresolved externals C:\Users\...\Documents\Visual Studio 2013\Projects\Double_Linked_List\Debug\Double_Linked_List.exe 1 Double_Linked_List </code></pre>

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