Error with template class

[Jack816]

#ifndef STACK_HPP_INCLUDED
#define STACK_HPP_INCLUDED
#include "NumStack.hpp"
 template <class T> class Stack : public NumStack
{
public:
   // Constructor
   Stack(T s) : NumStack(s) {}

   // MathStack operations
   void add();
   void sub();
   void mult();
   void div();
   void addAll();
   void multAll();
};

#endif // STACK_HPP_INCLUDED 

On line 5 I'm getting the error "expected class-name before '{' token". Could someone explain what I'm doing wrong?

[jlb]

Are there any other error messages? Please post the complete error message, all of them, exactly as they appear in your development environment.

How is NumStack defined?

[gunnerfunner]

is NumStack also template class/

[Jack816]

NumStack is also a template class.
NumStack.hpp

#ifndef NUMSTACK_HPP_INCLUDED
#define NUMSTACK_HPP_INCLUDED
template <class T> class NumStack
{
private:
   T *stackArray;  // Pointer to the stack array
   T stackSize;    // The stack size
   T top;          // Indicates the top of the stack

public:
   // Constructor
   NumStack(T);

   // Copy constructor
   NumStack(const NumStack &);

   // Destructor
   ~NumStack();

   // Stack operations
   void push(T);
   void pop(T &);
   bool isFull() const;
   bool isEmpty() const;
};

#endif // NUMSTACK_HPP_INCLUDED 

I do have a couple other errors. In the Stack<T> constructor I'm getting the error
"class 'Stack<T> does not have any field named 'NumStack'" In main it also says that I'm missing template arguments before 'stack'.
Here is my main

// This program demonstrates the MathStack class.
#include <iostream>
#include "stack.hpp"



int main()
{
   int catchVar;  // To hold values popped off the stack

   // Create a MathStack object.
   Stack stack(5);

   // Push 3 and 6 onto the stack.
   std::cout << "Pushing 3\n";
   stack.push(3);
   std::cout << "Pushing 6\n";
   stack.push(6);

   // Add the two values.
   stack.add();

   // Pop the sum off the stack and display it.
   std::cout << "The sum is ";
   stack.pop(catchVar);
   std::cout << catchVar << std::endl << std::endl;

   // Push 7 and 10 onto the stack
   std::cout << "Pushing 7\n";
   stack.push(7);
   std::cout << "Pushing 10\n";
   stack.push(10);

   // Subtract 7 from 10.
   stack.sub();

   // Pop the difference off the stack and display it.
   std::cout << "\nThe difference is ";
   stack.pop(catchVar);
   std::cout << catchVar << std::endl;

   std::cout << "\n\nPushing 5 then 10";
   stack.push(5);
   stack.push(10);
   std::cout << "\nThe product is ";
   stack.mult();
   stack.pop(catchVar);
   std::cout << catchVar;

   std::cout << "\n\nPushing 7 then 12";
   stack.push(7);
   stack.push(12);
   std::cout << "\nThe product is ";
   stack.mult();
   stack.pop(catchVar);
   std::cout << catchVar;

   std::cout << "\n\nPushing 14 and 2";
   stack.push(14);
   stack.push(2);
   std::cout << "\nThe quotient is ";
   stack.div();
   stack.pop(catchVar);
   std::cout << catchVar;

   std::cout << "\n\nPushing 24 and 12";
   stack.push(24);
   stack.push(12);
   std::cout << "\nThe quotient is ";
   stack.div();
   stack.pop(catchVar);
   std::cout << catchVar;

   std::cout << "\n\nPushing 24, 12, and 3";
   stack.push(24);
   stack.push(12);
   stack.push(3);
   std::cout << "\nThe sum is ";
   stack.addAll();
   stack.pop(catchVar);
   std::cout << catchVar;

   std::cout << "\n\nPushing 44, 47, and 1";
   stack.push(44);
   stack.push(47);
   stack.push(1);
   std::cout << "\nThe sum is ";
   stack.addAll();
   stack.pop(catchVar);
   std::cout << catchVar;

   std::cout << "\n\nPushing 24, 12, and 3";
   stack.push(24);
   stack.push(12);
   stack.push(3);
   std::cout << "\nThe product is ";
   stack.multAll();
   stack.pop(catchVar);
   std::cout << catchVar;

   std::cout << "\n\nPushing 18, 12, and 5";
   stack.push(18);
   stack.push(12);
   stack.push(5);
   std::cout << "\nThe product is ";
   stack.multAll();
   stack.pop(catchVar);
   std::cout << catchVar;

   return 0;
}

[doug4]

Try this:

#ifndef STACK_HPP_INCLUDED
#define STACK_HPP_INCLUDED
#include "NumStack.hpp"
 template <class T> class Stack : public NumStack<T> // added template arg to NumStack
{
public:
   // Constructor
   Stack(T s) : NumStack<T>(s) {}  // added template arg to Numstack

   // MathStack operations
   void add();
   void sub();
   void mult();
   void div();
   void addAll();
   void multAll();
};

#endif // STACK_HPP_INCLUDED  

[Jack816]

That fixed all, but one error. In main it still tells me that I'm missing the template arguments before 'stack'.

[gunnerfunner]

In main it also says that I'm missing template arguments before 'stack'.

you need to decide whether the derived class is also going to be a template class or not. At the moment the way you've laid out Stack in it's header file seems to suggest that it is a template class while in main() Stack is represented as a non-template class i.e. it is derived from a particular instantiation of NumStack<T>
if you want only NumStack to be template but not Stack it'd be something like:

template <typename T> class NumStack{};
class Stack : public NumStack<int>{};//Stack derived from NumStack<int> for e.g. 

Also NumStack is missing the template parameter here:
template <class T> class Stack : public NumStack // should be NumStack<T>

As for the other error message: "class 'Stack<T> does not have any field named 'NumStack'"
this is entirely reasonable given that NumStack<T> is expected to be a base for Stack(template or otherwise)

[Jack816]

Both classes need to be templates.
template <class T> class Stack : public NumStack<T>
I added NumStack<T>, but it still tells me that I'm missing template arguments.

[gunnerfunner]

Stack stack(5);
missing template arguments - Stack is non-template here

[Jack816]

Thanks, I'm new with templates and didn't realize that I had to add <int> in main.

[mbozzi]

In some cases the template arguments will be deduced, so you don't always (for function templates, anyways):
http://en.cppreference.com/w/cpp/language/template_argument_deduction

[Dz1T7k9E]

I'm doing a similar program and am having an error on line 21 of main.
I'm getting this error:

undefined reference to `Stack<int>::add()'

Can someone help me with this error?

[mbozzi]

Welcome to the forum!

You didn't define or link Stack<>::add(), or you tried to separate the implementation of Stack<>::add from it's declaration.

If you need more help, please open your own thread and post your code, instead of hijacking this one.