/*********************************************************
 * From C PROGRAMMING: A MODERN APPROACH, by K. N. King  *
 * Copyright (c) 1996 W. W. Norton & Company, Inc.       *
 * All rights reserved.                                  *
 * This program may be freely distributed for class use, *
 * provided that this copyright notice is retained.      *
 *********************************************************/

/* stack1.c (Chapter 19, page 424) */

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

#define STACK_SIZE 100

static int contents[STACK_SIZE];
static int top = 0;

void make_empty(void)
{
  top = 0;
}

int is_empty(void)
{
  return top == 0;
}

static int is_full(void)
{
  return top == STACK_SIZE;
}

void push(int i)
{
  if (is_full()) {
    printf("Error in push: stack is full.\n");
    exit(EXIT_FAILURE);
  }
  contents[top++] = i;
}

int pop(void)
{
  if (is_empty()) {
    printf("Error in pop: stack is empty.\n");
    exit(EXIT_FAILURE);
  }
  return contents[--top];
}