/*
 * An example for stack implemented in fix size array 
 */

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

#define SIZE 100

typedef struct {
	int data[SIZE];
	int top;    // 0 represent empty stack
} Stack;

void push(Stack* s, int data) {
	if (s->top == SIZE - 1) {
		fprintf(stderr, "overflow!\n");
		exit(1);
	}
	s->data[s->top++] = data;
}

int pop(Stack* s) {
	if (s->top == 0) {
		fprintf(stderr, "underflow!\n");
		exit(1);
	}
	return s->data[--s->top];
}

void init(Stack* s) {
	s->top = 0;
}

int top(Stack* s) {
	return s->data[s->top - 1];
}

int empty(Stack* s) {
	return s->top == 0;
}

int main() {

	Stack s;
	init(&s);

	push(&s, 1);
	printf("Top s is %d\n", top(&s));
	push(&s, 2);
	printf("Top s is %d\n", top(&s));
	pop(&s);
	printf("Top s is %d\n", top(&s));
	// w/o boundary checking
	/*   pop(&s); */
	/*   printf("Top s is %d\n", top(&s));   */
	/*   pop(&s); */
	/*   printf("Top s is %d\n", top(&s));   */
	pop(&s);
	printf("Top s is %d\n", top(&s));
	pop(&s);
	printf("Top s is %d\n", top(&s));

	return 0;
}