inline void print_tape() {
if (tape_changed) {
for (int i=0; i<tape.size(); i++)
cout << tape[i];
cout << endl;
}
}
inline void move_head(char move) {
if (move == 'l')
pos -= 1;
else if (move == 'r')
pos += 1;
else
throw string("unknown state");
if (pos < 0) {
tape.insert(tape.begin(), init);
pos = 0;
}
if (pos >= tape.size()) {
tape.push_back(init);
}
moves++;
}