why am i getting a clang: error: linker command failed with exit code 1 ( use -v to see invocation )

Question

I am working on a class assignment, relatively new to the c++ language and I have tried to function the code to hopefully get rid of the error but, have not been successful. can anyone help me out?, I am primarily working with mathstack template class and calling it to push a number to the stack but the following code comes up.

error message : clang++-7 -pthread -std=c++17 -o main MathStack.cpp main.cpp
/tmp/main-69d6a9.o: in function 'menu(int&)'; main.cpp:(.text+0x297): undefined reference to 
'MathStack<int>::push(int)'clang: error : linker command failed with code 1 (use -v to see 
invocation)


 

    **/ Implementation file for the MathStack class**
#include "MathStack.h"
#include <iostream>

//***********************************************
// Member function add. add pops                *
// the first two values off the stack and       *
// adds them. The sum is pushed onto the stack. *
//***********************************************
template <class T>
void MathStack<T>::add()
{
   T num, sum;

   // Pop the first two values off the stack.
   pop(sum);
   pop(num);

   // Add the two values, store in sum.
   sum += num;

   // Push sum back onto the stack.
   push(sum);
}

//***********************************************
// Member function sub. sub pops the            *
// first two values off the stack. The          *
// second value is subtracted from the          *
// first value. The difference is pushed        *
// onto the stack.                              *
//***********************************************
template <class T>
void MathStack<T>::sub()
{
   T num, diff;

   // Pop the first two values off the stack.
   pop(diff);
   pop(num);

   // Subtract num from diff.
   diff -= num;

   // Push diff back onto the stack.
   push(diff);
}

//**********************************************
// Member function mult. multiplies first two  *
// values of the stack.                        *
//**********************************************
template <class T>
void MathStack<T>::mult()
{
T num, res;

// pop the first two values of the stack
pop(res);
pop(num);

// multiply thw two values
res = res*num;

// push result back into the stack
push(res);
}
template <class T>

//*********************************************
// Member funciton div. divides the first two *
// values of the stack.                       *
// shows an error when divided by zero        *
//*********************************************


void MathStack<T>::div()
{
 T quot, divisor;

// pop the first two values of the stack
 pop(divisor);
 pop(quot);


 // exexption 
 if (divisor == 0)
 {
    cout << "ERROR: Cannot divide by zero.\n"; 
 }
    else {quot = quot/divisor; } // division formula 

// push quotient back into the stack
 push(quot);
}



//*************************************************
// Member function push pushes the argument onto  *
// the stack.                                     *
//*************************************************

template <class T>
void MathStack<T>::push(T num)
{
   if (isFull())
   {
      cout << "The stack is full.\n";
   }
   else
   {
      top++;
      stackArray[top] = num;
   }
}

//****************************************************
// Member function pop pops the value at the top     *
// of the stack off, and copies it into the variable *
// passed as an argument.                            *
//****************************************************


template <class T>
void MathStack<T>::pop(T &num)
{
   if (isEmpty())
   {
      cout << "The stack is empty.\n";
   }
   else
   {
      num = stackArray[top];
      top--;
   }
}

//***************************************************
// Member function isFull returns true if the stack *
// is full, or false otherwise.                     *
//***************************************************

template <class T>
bool MathStack<T>::isFull() const
{
   bool status;

   if (top == stackSize - 1)
      status = true;
   else
      status = false;

   return status;
}

//****************************************************
// Member funciton isEmpty returns true if the stack *
// is empty, or false otherwise.                     *
//****************************************************

template <class T>
bool MathStack<T>::isEmpty() const
{
   bool status;

   if (top == -1)
      status = true;
   else 
      status = false;

   return status;
}
         





   // file specifies the stack class and use of math functions
#include <iostream>
#include "MathStack.h"
using namespace std;

// Constants for the menu choices
const int Add = 1,
          Subtract = 2,
          Multiply = 3,
          Division = 4,
          QUIT = 5;

// Function prototypes
void menu(int &);
void getStackSize(int &);

int main()
{
    int stackSize; // The stack size
    int choice;    // To hold a menu choice
    

     menu(choice);
  
    // Create the stack.
    MathStack<int> Math(stackSize);
    MathStack<float> Math1(stackSize);
  

    return 0;
}

//************************************************
// The menu function displays the menu and gets  *
// the user's choice, which is assigned to the   *
// reference parameter.                          *
//************************************************
void menu(int &choice)
{    
    int stackSize;      
    int number;
    getStackSize(stackSize);     
     // Display the menu and get the user's choice.
     cout << "\nWhat do you want to do?\n"
          << Add
          << " - Add items from the stack\n"
          << Subtract
          << " - Subtact items from the stack\n"
          << Multiply
          << " - Multiply items from the stack\n"
          << Division
          << " - Divide items form the stack\n"
          << QUIT
          << " - Quit the program\n"
          << "Enter your choice: ";
     cin >> choice;
     
     // Validate the choice
     while (choice < Add || choice > QUIT)
     {
        cout << "Enter a valid choice: ";
        cin >> choice;
     }
    switch(choice)
    {
      case 1: 
       MathStack<int> Math(stackSize);
       for (int i = 0; i < stackSize; i++)
       {
        cout << " Enter number to insert to the stack:\n" << endl;
       }
       cin >> number;
       Math.push(number);
    }
}
//************************************************
// The getStackSize function gets the desired    *
// stack size, which is assigned to the          * 
// reference parameter.                          *
//************************************************
void getStackSize(int &size)
{
     // Get the desired stack size.
     cout << "How big should I make the stack? ";
     cin >> size;
     
     // Validate the size.
     while (size < 1)
     {
           cout << "Enter 1 or greater: ";
           cin >> size;
     }
}