#include "c1_stack.h"

// initialize data structure
void stack_create(Stack *s) {
	s->index = -1;
	s->elements = (int *) malloc(MAX_ELEMENTS * sizeof(int));
}

// remove data allocated by stack_create
void stack_delete(Stack *s) {
	free(s->elements);
}

// push
void stack_push(Stack *s, int v) {
	++s->index;
	if (s->index == MAX_ELEMENTS) {
		printf("stack is full\n");
		exit(1);
	}
	s->elements[s->index] = v;
}

// pop
void stack_pop(Stack *s) {
	if (s->index == -1) {
		printf("stack is empty\n");
		exit(1);
	}
	--s->index;
}

// return element on top
int stack_top(Stack *s) {
	if (s->index == -1) {
		printf("stack is empty\n");
		exit(1);
	}
	return s->elements[s->index];
}

// return 1 if stack is empty, 0 otherwise
int stack_is_empty(Stack *s) {
	return (s->index == -1) ? 1 : 0;
}

// main
int main() {
	int i, sum = 0;
	Stack s;
	
	stack_create(&s);
	for (i = 1; i<=10; ++i) {
		stack_push(&s, i);
	}
	
	while  (!stack_is_empty(&s)) {
		sum += stack_top(&s);
		stack_pop(&s);
	}
	
	printf("sum = %d\n", sum);
	
	stack_delete(&s);
	return 0;
}