/*
 * the stack module
 */
#include <stdio.h>
#include "stack.h"

static int stack[STACKSIZE];	/* the stack itself */
static int top = -1;	/* index of top element of stack; -1 is empty */

/*
 * push a value onto the stack
 * exits on stack overflow
 */
void push(int val)
{
	/* check for overflow */
	if (top >= STACKSIZE-1){
		fprintf(stderr, "Stack is full\n");
		return;
	}
	/* push onto stack */
	stack[++top] = val;
	return;
}

/*
 * pop a value from the stack
 * exits on stack underflow
 */
int pop(int *val)
{
	/* check for an empty stack */
	if (top < 0){
		fprintf(stderr, "Stack is empty\n");
		return(0);
	}
	/* pop from stack */
	*val = stack[top--];
	return(1);
}


/*
 * print the top of the stack and the elements on the stack
 */
void printstack(void)
{
	int i;			/* used to walk the stack */

	/* print the top index */
	printf("top = %d\n", top);

	/* now print the elements of the stack, top down */
	for(i = top; i >= 0; i--)
		printf("%3d: %10d\n", i, stack[i]);
}