#include "stack.h"
#include <assert.h>
#include <stdlib.h>

stack_t init_stack(void)
{
	stack_t s;
	s.p = malloc((s.cap = 128) * sizeof(int));
	assert(s.p);
	s.top = -1;
	return s;
}

void push(stack_t *stack, int v)
{
	if (stack->top >= stack->cap) {
		stack->p = realloc(stack->p, (stack->cap += 128) * sizeof(int));
		assert(stack->p);
	}
	stack->top++;
	stack->p[stack->top] = v;
}

int pop(stack_t *stack)
{
	return stack->p[stack->top--];
}

int empty(stack_t stack)
{
	return stack.top < 0;
}

int top(stack_t stack)
{
	return stack.p[stack.top];
}

void free_stack(stack_t *s)
{
	if (s->p)
		free(s->p);
	s->p = NULL;
}