C++ :: Stack Implementation With Struct

I am trying to implement a stack class which has struct data type as its private member. I am getiing the following error ,

bash-3.2$ g++ stack_str_arr.cpp
stack_str_arr.cpp: In member function ‘void stack::push(int)’:
stack_str_arr.cpp:39: error: ‘top’ was not declared in this scope
stack_str_arr.cpp: At global scope:
stack_str_arr.cpp:43: error: no ‘void stack::display()’ member function declared in class ‘stack’

Code:

#include<iostream>
using namespace std;
#define MAX 5
class stack {
public :
stack();

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