17 struct Tape {  struct
18   constexpr Tape() : l(0), val(false), r(0) {}  in Tape()  function
19   constexpr Tape(const Tape &old, bool write) :  in Tape()  function
21   constexpr Tape(const Tape &old, Dir dir) :  in Tape()  function
26   const Tape *l;  argument
28   const Tape *r;  argument
30 constexpr Tape update(const Tape &old, bool write) { return Tape(old, write); }  in update()
31 constexpr Tape move(const Tape &old, Dir dir) { return Tape(old, dir); }  in move()
35 constexpr unsigned run(const State *tm, const Tape &tape, unsigned state) {  in run()
48 static_assert(run(bb3, Tape(), 0) == 21, "");
56 static_assert(run(bb4, Tape(), 0) == 107, "");