#ifndef _COMMON_H_
#define _COMMON_H_

#define SIZE 1024
#define BROKEN_HEART 1
#define CONS 2
#define INTEGER 3
#define SYMBOL 4
#define BYE 5

typedef struct box_t {
  char type;
  union {
    int integer;
    char* symbol;
    struct cons_t* cons;
  };
} box_t;

typedef struct cons_t {
  box_t car;
  box_t cdr;
} cons_t;

extern cons_t *the_empty_list;

#endif // _COMMON_H_