/*
 * ISA 563, Spring 2011
 * Copyleft by Muhammad Abdulla
 */

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

#include "stack4.h"

#define S Stack 

#define MAX 100

struct S
{
   int stack[MAX];
   int stack_idx;
}; 

S stack_new()
{
   S s;

   s = ( S ) malloc ( sizeof ( *s ) ) ;
   assert(s != NULL);

   s->stack_idx = 0;

   return s;
}

void stack_push(S s, int item)
{
   if ( s->stack_idx < MAX ) {
      s->stack[(s->stack_idx)++] = item;
   } else {
      fprintf(stderr, "stack is full, returning.\n");
   }
}

int stack_pop(S s)
{
   if ( s->stack_idx > 0 ) {
      return s->stack[--(s->stack_idx)]; 
   } else {
      fprintf(stderr, "stack is empty, returning -1.\n");
      return -1;
   }
}

int stack_empty(S s)
{
   return s->stack_idx > 0 ? 0 : 1;
}

int stack_full(S s)
{
   return s->stack_idx < MAX ? 0 : 1;
}

void stack_free(S s)
{
   if ( ! s ) {
      return;
   }

   free(s);
}