#include "stack.h"
#ifdef DEBUG
#include <stdio.h>
static int nelem = 0;
#endif DEBUG

int isempty( TOP t) { return (t == NULLVAL); }

DATA top(TOP t) { return (t -> d); }

void pop(TOP *t, DATA *x) { TOP t1 = *t;
#ifdef DEBUG
	extern int nelem;
#endif DEBUG
	
	if(! isempty(t1) ){
		*x = t1->d;
		*t = t1->next;
		free(t1);
#ifdef DEBUG
		nelem--;
		printf("leaving pop nelem = %d\n",nelem);
#endif DEBUG
	}
	else
		printf("\npop: empty stack\n");
}

void push( TOP *t, DATA x) { TOP temp;
#ifdef DEBUG
	extern int nelem;
#endif DEBUG
	
	temp = (TOP) malloc(sizeof(ELEMENT));
	temp->d = x;
	temp->next = *t;
	*t = temp;
#ifdef DEBUG
	nelem++;
	printf("leaving push nelem = %d\n",nelem);
#endif DEBUG
}