struct value {
  int type;
  struct value *next;           /* Linked list of values. */
  union {
    char *string;
    int number;
    struct lnode *ref;
    struct object *ob;
  } u;
};

#define T_INVALID   0
#define T_NUMBER    1
#define T_STRING    2
#define T_REFERENCE 3
#define T_OBJECT    4

extern struct value const0, const1;