#ifndef _VECTOR_H_
#define _VECTOR_H_
#include <stdlib.h>
#include <stdio.h>

struct vec
{
    int *list;
    int size;
    int index;
};

#define VEC_NEEDS_RESIZE(vec) (((vec)->index + 1) == (vec)->size)

void* vec_resize (void* items, size_t new_size)
{
    void *new_items = realloc(items, new_size);
    if (new_items == NULL) perror("vec_resize");
    return new_items;
}

#define VEC_PUSH(vec, item) do {\
    if (VEC_NEEDS_RESIZE(vec)) { \
		(vec)->size *= 2; \
        (vec)->list = vec_resize((vec)->list, (vec)->size * sizeof(item)); \
	} \
	\
	(vec)->list[(vec)->index++] = item; } while (0)

#define VEC_INIT(vec, items) \
	(vec)->list = calloc(items, sizeof(__typeof__(*((vec)->list)))); \
	(vec)->size = items; \
	(vec)->index = 0

#define VEC_DESTROY(vec) \
	free((vec)->list); \
	(vec)->list = NULL; \
	(vec)->index = (vec)->size = 0;

#endif