Pushing and Popping my own Stack

[Edgy]

I dont know how to properly make and push/pop my own user created stack. I have to have a user created one as a parameter.

For example the lines,

topNum = stackArray.top();
stackArray.pop(top);
secondNum = stackArray.top();
stackArray.pop(top);

do not work and give me the error "Expression preceding parentheses must have
pointer to function.

IntStack.h

#ifndef INTSTACK_H_
#define INTSTACK_H_

class IntStack
{
private:
	int *stackArray;
	int stackSize;
	int top;

public:
	// constructor
	IntStack(int);
	// copy constructor
	IntStack(const IntStack &);

	// destructor
	~IntStack();

	// stack operations
	void push(int);
	void pop(int &);
	bool isFull() const;
	bool isEmpty()const;
};


#endif /* INTSTACK_H_ */ 

IntStack.cpp

#include <iostream>
#include "IntStack.h"

using namespace std;


// constructor
IntStack::IntStack(int size)
{
	stackArray = new int[size];
	stackSize = size;
	top = -1;
}

// copy constructor
IntStack::IntStack(const IntStack &obj)
{
	// stack array
	if (obj.stackSize > 0)
		stackArray = new int[obj.stackSize];
	else
		stackArray = 0;

	// copy stackSize to obj class attributes
	stackSize = obj.stackSize;

	//copy stack
	for (int i = 0; i < stackSize; i++)
	{
		stackArray[i] = obj.stackArray[i];
	}

	//copy top of the stack
	top = obj.top;
}

// destructor
IntStack::~IntStack()
{
	delete[] stackArray;
}

// functions to push and pop the stack, will provide warning if the stack is full or empty
void IntStack::push(int num)
{
	if (isFull())
	{
		cout << "Error: The stack is full.\n";
	}
	else
	{
		top++;
		stackArray[top] = num;
	}
}

void IntStack::pop(int &num)
{
	if (isEmpty())
	{
		cout << "Error: The stack is empty. \n";
	}
	else
	{
		num = stackArray[top];
		top--;
	}
}

bool IntStack::isFull() const
{
	bool status;

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

	return status;
}

bool IntStack::isEmpty() const
{
	bool status;

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

	return status;


}

main.cpp

#include <iostream>
#include <string.h>
#include <stack>
#include <sstream>
#include <stdlib.h>
#include "IntStack.h"

using namespace std;

int main()
{
	char input;
	// determine which stack method user wants to use
	cout << "Welcome to my postfix notation calculator. \n";
	cout << "Do you wish to: \n";
	cout << "0) Use my own implementation of a stack. \n";
	cout << "1) Use an STL stack. \n";
	cin >> input;
	while (input != '0' && input != '1')
	{
		cout << "Please enter the number 0 or 1: ";
		cin >> input;
	}

	// if the user picks my stack to calculate the result
	if (input == '0')
	{
		//create the stack to be used
		IntStack stackArray(25);
		int i, num, result, topNum, secondNum;
		char op, ch;
		string str, str1;
		cout << "You have chosen to use my stack. \n";
		cout << "Please enter your calculation in reverse polish notation: ";

		cin.ignore();
		getline(cin, str);
		
		istringstream is(str);

		int size = str.size();
		char charArr[100];

		// create char array of the string
		for (int i = 0; i <= size; i++)
		{
			charArr[i] = str[i];
		}
		

		// read code , adding it to stack and preforming operations when an operator is reached
			for (; is >> str1;){

			if (str1.compare("+") == 0){

				topNum = stackArray.top();
				stackArray.pop(top);
				secondNum = stackArray.top();
				stackArray.pop(top);

				stackArray.push(topNum + secondNum);

			}
			else if (str1.compare("-") == 0){

				topNum = stackArray.top();
				stackArray.pop(top);
				secondNum = stackArray.top();
				stackArray.pop(top);
				stackArray.push(secondNum - topNum);
			}
			else if (str1.compare("*") == 0){

				topNum = stackArray.top();
				stackArray.pop(top);
				secondNum = stackArray.top();
				stackArray.pop(top);
				stackArray.push(topNum * secondNum);
			}
			else if (str1.compare("/") == 0){

				topNum = stackArray.top();
				stackArray.pop(top);
				secondNum = *stackArray.top();
				stackArray.pop(top);
				stackArray.push(secondNum / topNum);
			}
			// if there was no operator push the number onto the stack
			else{

				stackArray.push(strtof(str1.c_str(), NULL));
			}
		}

		cout << "The answer is:" << stackArray.top();
	}


	// if the user picks to use the standard template library
	else
	{
		cout << "You have chosen the STL library \n";
		cout << "Please enter your calculation in reverse polish notation: ";
		
		// create STL stack
		stack<int>stack;
		int i, num, result, topNum, secondNum;
		char op, ch;
		string str, str1;

		// get the line as a string
		cin.ignore();
		getline(cin, str);
		istringstream is(str);

		// read code , adding it to stack and preforming operations when an operator is reached
		for (; is >> str1;){

		if (str1.compare("+") == 0){

		topNum = stack.top();
		stack.pop();
		secondNum = stack.top();
		stack.pop();


		stack.push(topNum + secondNum);

		}
		else if (str1.compare("-") == 0){

		topNum = stack.top();
		stack.pop();
		secondNum = stack.top();
		stack.pop();
		stack.push(secondNum - topNum);
		}
		else if (str1.compare("*") == 0){

		topNum = stack.top();
		stack.pop();
		secondNum = stack.top();
		stack.pop();
		stack.push(topNum * secondNum);
		}
		else if (str1.compare("/") == 0){

		topNum = stack.top();
		stack.pop();
		secondNum = stack.top();
		stack.pop();
		stack.push(secondNum / topNum);
		}
		// if there was no operator push the number onto the stack
		else{

		stack.push(strtof(str1.c_str(), NULL));
		}
		}

		cout << "The answer is:" << stack.top();
		}

		

		return 0;
	
}