/* 

Sandra N. Kardaras-Flick
03/16/05

STACKS
A program which allows the user to input integers, and returns those 
integers reversed.

*/


#include <stdio.h>
#include <stdlib.h>

#define STACK_SIZE 50
#define TRUE 1
#define FALSE 0

typedef int boolean;

void makeEmptyStack(void);
boolean stackIsEmpty(void);
boolean stackIsFull(void);

void push(int i);
int pop(void);

void stackOverflow(void);
void stackUnderflow(void);

int contentsOfStack[STACK_SIZE];
int *top_ptr = &contentsOfStack[0];

int main()

{

  int temp = 0;

  makeEmptyStack();
  printf("\n\n\n\n\t Numeric entry:\t");

		while ((temp = getchar()) != '\n')
	
		{
	
			if (isdigit(temp)) 
	
			{
		
				temp = temp - '0';
				push(temp);
		
			}
		
		}


  printf("Numeric entry reversed:\t");

	  while (!stackIsEmpty()) 
	  
	  {
    	
			printf("%d", pop());
			
  		}
  
  printf("\n\n\n\n");

return 0;

}



	void makeEmptyStack(void)

	{
	
		top_ptr = &contentsOfStack[0];
	
	}

	
	
	boolean stackIsEmpty(void)
	
	{
	
		return top_ptr == &contentsOfStack[0];
	
	}



	boolean stackIsFull(void)
	
	{
	
		return top_ptr == &contentsOfStack[STACK_SIZE];
	
	}

	

	void push(int i)
	
	{
 
    if (stackIsFull())
        stackOverflow();
		  else
        *top_ptr++ = i;

	}



	int pop(void)
	
	{
 
    if (!stackIsEmpty())
 	   return *--top_ptr;
		
		else
        stackUnderflow();

    return 0;
	}



	void stackOverflow(void)

	{
	
		printf("\nStack Overflow\n");
		exit(EXIT_FAILURE);
	
	}



	void stackUnderflow(void)
	
	{
		
		printf("\nStack Underflow\n");
		exit(EXIT_FAILURE);
	
	}