Problems with c++ templates

From:
"Mr B" <mrb_16@hotmail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
21 Oct 2006 16:51:52 -0400
Message-ID:
<1161448728.805374.248670@e3g2000cwe.googlegroups.com>
Hi all,

I'm currently studying templates in C++ and i'm really puzzled by why
the compiler doesn't like my code!!! I think I understand the concept.
I have created a Stack class which has a pointer to a Node class. The
Node class stores a value and a pointer to the previously added node.
My code is below:

//------------------------------------------------------------------------------
template <typename T>
class Node
{
   friend class MyStack;

   private:
         Node *PreviousNode;
         T NodeVal;

   public:
         Node(T InitVal);
         T GetVal() { return NodeVal; }
};

//------------------------------------------------------------------------------
template <typename T>
Node<T>::Node(T InitVal)
{
   NodeVal = InitVal;
   PreviousNode=NULL;
}
//------------------------------------------------------------------------------
template <typename DT>
class MyStack
{
   private:
         Node<DT> *TopNode;
         int MaximumNodes;
         int NumNodes;

   public:
         MyStack(int Size);
         ~MyStack();
         void Push(DT Val);
         DT Pop();
};
//------------------------------------------------------------------------------
MyStack::MyStack(int Size)
{
   MaximumNodes = Size;
   NumNodes=0;
   TopNode = NULL;
}
//------------------------------------------------------------------------------
MyStack::~MyStack()
{
   while(NumNodes > 0)
   {
     Pop();
   }
}
//------------------------------------------------------------------------------

template <typename DT>
void MyStack<DT>::Push(DT Val)
{
   Node *NewNode;

   if (NumNodes < MaximumNodes)
   {
     NewNode = new Node(Val);

     NewNode->PreviousNode = TopNode;
     TopNode = NewNode;

     NumNodes++;
   }
   else { throw "Stack Overflow error"; }
}
//------------------------------------------------------------------------------
template <typename DT>
DT MyStack<DT>::Pop()
{
   Node *Popped;
   DT PopVal;

   if(NumNodes >= 1)
   {
     Popped = TopNode;
     TopNode = TopNode->PreviousNode;
     PopVal=Popped->GetVal();

     delete Popped;
     NumNodes--;

     return PopVal;
   }
   else { throw "Stack Underflow error"; }
}
//------------------------------------------------------------------------------

void main()
{
   try
   {
     MyStack <int>*NewStack = new MyStack<int>(5);
     NewStack->Push(6);
     NewStack->Push(30);
     NewStack->Push(2);
     NewStack->Push(4);
     NewStack->Push(7);
     cout << NewStack->Pop() << "\n";
     cout << NewStack->Pop() << "\n";
     cout << NewStack->Pop() << "\n";
     cout << NewStack->Pop() << "\n";
     cout << NewStack->Pop() << "\n";
   }

   catch (char *Str)
   {
     puts(Str);
   }

   delete NewStack;

   getchar();
}

Amongst errors I get a 'Type mismatch in redeclaration of 'MyStack''
Could somebody please tell me where i'm going wrong!!

Thanks

Daniel

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