#include <stdint.h>
#include <stdlib.h>
#include <assert.h>

struct stack;

enum node_tag {
    NODE_APP,
    NODE_NUM,
    NODE_GLOBAL,
    NODE_IND,
    NODE_PACK
};

struct node_base {
    enum node_tag tag;
};

struct node_app {
    struct node_base base;
    struct node_base* left;
    struct node_base* right;
};

struct node_num {
    struct node_base base;
    int32_t value;
};

struct node_global {
    struct node_base base;
    void (*function)(struct stack*);
};

struct node_ind {
    struct node_base base;
    struct node_base* next;
};

struct node_data {
    struct node_base base;
    int8_t tag;
    struct node_base** array;
};

struct node_base* alloc_node() {
    node_base* new_node = malloc(sizeof(struct node_app));
    assert(new_node != NULL);
    return new_node;
}