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POerror C2079: 'stackNameSpace::StackNode<T>::value' uses undefined class
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16113679
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0
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2
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2
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2013-04-19T21:21:51.183
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2013-04-20T06:24:33.207
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2300170
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the interface of Stack.h <pre><code>#include "stdafx.h" //use linkedlist to implement the stack //which is different from using the array to implement the stack #ifndef STACK_H #define STACK_H using namespace std; namespace stackNameSpace { template<class T> struct StackNode { T value; T min_value; //current local min value StackNode* next; }; typedef StackNode<class T>* StackNodePtr; template<class T> class Stack { private: StackNodePtr top; public: Stack(); Stack(const Stack& a_stack); ~Stack(); bool empty() const; T pop(); void push(T the_value); T getMin(); }; } //end of namespace #endif </code></pre> The implementation of the stack.h <pre><code>#include "stdafx.h" //use linkedlist to implement the stack //which is different from using the array to implement the stack #ifndef STACK_CPP #define STACK_CPP #include <iostream> #include <cstdlib> #include "Stack.h" using namespace std; namespace stackNameSpace { template<class T> Stack<T>::Stack() : top(NULL) //here should be Stack<T> instead of Stack {} template<class T> Stack<T>::Stack(const Stack& a_stack) { if (a_stack.top == NULL) { return NULL; } else { StackNodePtr currentOld = a_stack.top; //construct the top of the new stack StackNodePtr currentNew = new StackNode<class T>;//the struct currentNew->value = currentOld->value; currentNew->min_value = currentOld->min_value; top = currentNew; //contruct the rest node in the stack currentOld = currentOld->next; while (currentOld != NULL) { currentNew->next = new StackNode<class T>; currentNew = currentNew->next; currentNew->value = currentOld->value; currentNew->min_value = currentOld->min_value; currentOld = currentOld->next; } currentOld->next = NULL; } } template<class T> Stack<T>::~Stack() { T data; while (!empty()) { data = pop(); } } template<class T> bool Stack<T>::empty() const { return (top == NULL); } template<class T> T Stack<T>::pop() { if (empty()) { cout << "Error: popping an empty stack.\n"; exit(1); } T result = top->value; StackNodePtr temp = new StackNode<class T>; temp = top; top = top->next; delete temp; return result; } template<class T> void push(T the_value) { StackNodePtr temp = new StackNode<class T>; temp->value = the_value; temp->min_value = min(the_value, getMin());//This is Much better //temp->min_value = top->min_value; //This is NOT secure, since top may be NULL temp->next = top; //update the top node top = temp; } template<class T> T getMin() { if (top == NULL) return INT_MAX; else { return top->min_value; } } } //end of namespace #endif </code></pre> The function using the Stack class <pre><code>#include "stdafx.h" #include <iostream> #include "Stack.h" //this is not the <stack>, which is STL //using namespace std; //NOTE: this must be wrong! because can not use multiple namespace at the same time using namespace stackNameSpace; using std::cout; using std::endl; int main() { Stack<int> sWithMin; sWithMin.push(5); cout<< sWithMin.getMin() << endl; sWithMin.push(4); cout<< sWithMin.getMin() << endl; sWithMin.push(5); cout<< sWithMin.getMin() << endl; sWithMin.push(3); cout<< sWithMin.getMin() << endl; sWithMin.push(6); cout<< sWithMin.getMin() << endl; return 0; } </code></pre> When I compile the project, I get an error in main() that "error C2079: 'stackNameSpace::StackNode::value' uses undefined class 'stackNameSpace::T'" I can not figure out the reason why it has the error. Could anyone please help me?
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error C2079: 'stackNameSpace::StackNode<T>::value' uses undefined class
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1. COpossible duplicate of [Why can templates only be implemented in the header file?](http://stackoverflow.com/questions/495021/why-can-templates-only-be-implemented-in-the-header-file)
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 POerror C2079: 'stackNameSpace::StackNode<T>::value' uses undefined class
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 USAndy Prowl
2. COThis is not just the template not in header problem.
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 POerror C2079: 'stackNameSpace::StackNode<T>::value' uses undefined class
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 USJoergB

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