Help fix postfix expression pgm

[l3ecl]

My program evaluates a postfix expression. I'm trying to edit my code so that the user does not need to enter the equal sign '=' as part of the input. I have two solutions but am having a very hard time implementing either of them. I can either: input the '=' for the user, or implement an EOF to act as the equal sign. Please help me implement either of these.

below is my code:

//This programm is post fix calculator
#include "stdafx.h" 
#include <iostream> 
using namespace std; 

struct pq {

	char st[15]; 
	pq *next;

};

struct es 
{
	int value; 
	es* next;

};


bool is_integer(char answer[]); 
es *push(es *h, int n); 
es *pop_es_head(es *es_head);
pq *pop_pq_head(pq *head);
void printlistpq(struct pq *p);
void printlistes(struct es *e);


int main() 
{
	pq *head, *current, *temp; 
	string s;

	head = new pq; 
	cout << "Enter the number and signs"<<endl; 
	cin >> head->st;

	if(head->st[0] != '=') 
	{
		head->next = NULL;
		current = head;
		temp = new pq; 
		cin >> temp->st;

		while(temp->st[0] != '=') 
		{
			temp->next = NULL;
			current->next = temp;
			current = current->next;
			temp = new pq; 
			cin >> temp->st;
		}
		delete temp; 
	}
	printlistpq(head);
	es *es_head; 
	bool integer; 
	int result; 
	integer = is_integer(head->st);

	if(integer == true) 
	{
		es_head = new es; 
		es_head->value = atoi(head->st);
		es_head->next = NULL;
		temp = head->next;
		delete head; 
		head = temp;

		while(head != NULL) 
		{
			integer = is_integer(head->st);
			if(integer == true) 
			{
				es_head = push(es_head, atoi(head->st));
				printlistpq(head);
			}
			else 
			{
				switch(head->st[0])
				{
				case '+': 
					result = es_head->value + es_head->next->value; 
					printlistpq(head);
					es_head = pop_es_head(es_head);
					es_head = pop_es_head(es_head);
					es_head = push(es_head, result);
					break; 
				case '-': 
					result = es_head->next->value - es_head->value; 
					printlistpq(head);
					es_head = pop_es_head(es_head);		
					es_head = pop_es_head(es_head);	
					es_head = push(es_head, result);
					break; 
				case '*': 
					result = es_head->value * es_head->next->value; 
					printlistpq(head);
					es_head = pop_es_head(es_head);
					es_head = pop_es_head(es_head);
					es_head = push(es_head, result);
					break; 
				case '/': 
					result = es_head->next->value / es_head->value; 	
					printlistpq(head);
					es_head = pop_es_head(es_head);
					es_head = pop_es_head(es_head);
					es_head = push(es_head, result);
					break; 
				default: cout << "Invalid operator.";
				} 
			} 
			head = pop_pq_head(head);
		} 

	} 
	printlistpq(head);
	if (head == NULL) 
	{
		cout << "The answer is " << es_head->value << "."; 
	} 
	system("pause");
	return 0; 
}



bool is_integer(char answer[])         //  checks the input contains non-integer characters.
{
	bool integer = true; 
	int len = int(strlen(answer)); 

	for (int i = 0; i < len; i++) 
	{
		if (answer[i] <= '9' && answer[i] >= '0') 
			integer = true; 
		else 
		{
			integer = false; 
			break; 
		}
	}
	return integer; 
} 



es *push(es *h, int n)  // pushes values into the evaluation stack
{
	es *temp;
	temp = h;
	h = new es; 
	h->value = n;
	h->next = temp;
	return h; 
}


es *pop_es_head(es *es_head)     // pops the head of the evaluation stack
{
	es *es_temp;
	es_temp = es_head->next;
	delete es_head; 
	es_head = es_temp;
	return es_head; 
}



pq *pop_pq_head(pq *head)         // pops the head of the polish queue
{
	pq *temp;
	temp = head->next;
	delete head; 
	head = temp;
	return head; 
} 

void printlistpq(struct pq *p)
{
	struct pq *listptr=p;

	cout<<"the polish queue is :\n";
	while(listptr!=0)
	{
		cout<<listptr->st<<endl;
		listptr=listptr->next;
	}
}

void printlistes(struct es *e)
{
	struct es *list=e;

	cout<<"the evaluation stack is :\n";
	while(list!=0)
	{
		cout<<list->value<<endl;
		list=list->next;
	}
}