#include "stdio.h"
#include "stdlib.h"

typedef struct node {
	float data;
	node *prox;
	node *prev;
} node;

typedef struct {
	int size;
	node *base;
	node *top;
} stack;

void initStack(stack *s) {
	s->base = s->top = NULL;
	s->size = 0;
}

node *createNode(float data) {
	node *n;
	n = (node*)malloc(sizeof(node));
	n->prev = n->prox = NULL;
	n->data = data;
	return n;
}

void push(stack *s, float data) {
	node *n = createNode(data);
	if (s->size == 0) 
		s->base = s->top = n;
	else {
		n->prev = s->top;
		s->top->prox = n;
		s->top = n;
	}
	s->size++;
}

float pop(stack *s) {
	if (s->size == 0) 
		return 0;
	else {
		node *t = s->top;
		float data = s->top->data;
		s->top = s->top->prev;
		if (s->top != NULL)
			s->top->prox = NULL;
		s->size--;
		free(t);
		return data;
	}

}

void showStack(stack *s) {
	node *t;
	t = s->base;
	while (t != NULL)
	{
		printf("%f\n", t->data);
		t = t->prox;
	}

}

int main() {

	stack s;
	initStack(&s);

	push(&s, 1);
	push(&s, 2);
	push(&s, 3);

	showStack(&s);

	printf("%f \n", pop(&s));
	printf("%f \n", pop(&s));
	printf("%f \n", pop(&s));
	printf("%f \n", pop(&s));

	return 0;
}