struct string_t {
  lu64     len;
  lu8[len] ptr;
};
struct strpair_t {
  string_t key;
  string_t value;
};

enum sex_t {
  SEX_MALE   = 0x0,
  SEX_FEMALE = 0x1,
  SEX_CAT    = 0x2,
};

enum role_t {
  ROLE_TEACHER = 0x0,
  ROLE_STUDENT = 0x1,
};

struct date_t {
  lu8 mon;
  lu8 day;
};

struct teacher_t {
  lu32   salary;
  date_t payday;
};

struct student_t {
  lu8[(1 << 4) - 6] scores;
  lu8 absents;
};

struct user_t {
  string_t name;
  lu8      age;
  lu8      sex;   /* sex_t */
  lu8      role;  /* role_t */

  lu16                      property_count;
  strpair_t[property_count] properties;

  union {
    (role == ROLE_TEACHER) teacher_t teacher;
    (role == ROLE_STUDENT) student_t student;
  };
};