23. Refinements: part 2

Here’s the cause of the problem we had at the end of part 1: we put down a token and, before we had the chance to move, tested to see if we were not next to a token. Since we were next to a token, we never go the chance to get in the while loop. Perhaps we can change the program to add a move() before we start the loop, as follows:

put("token");
move();
while ( !token_here() ){
    if (front_is_clear()){
        move();
    } else {
        turn_left();
    }
}

Try it!

Make sure the above program works before moving on.

23.1. Not so simple world

Let’s try the program we wrote on a slightly more complicated world Around 2.

When you try your program, you will see that the result is not exactly what we wanted: Reeborg takes a shortcut, and doesn’t go all the way around. The problem is that we assumed that Reeborg only had to move forward or turn left to go around the world; we never took into account situations where we would have wanted him to make a right turn. What Reeborg needs to do is first to check on his right to see if there is still a wall; if not, we have him make a right turn. Here’s a modified program that attempts to do just that:

put("token");
move();
while ( !token_here() ){
    if (right_is_clear()){
        turn_right();
    } else if (front_is_clear()){
        move();
    } else {
        turn_left();
    }
}

Your turn!

Does it work? Read it carefully to decide for yourself. Then try it to confirm your opinion by running the program, or make any change you think appropriate.