>General sort of question:
>
>I'm drawing a compass and need to determine the 'shortest' direction in which to rotate the compass (clockwise or anti-clockwise) between old and new bearings (in degrees).
>In most cases it is simple but when the old and new values span the 0 degree point those solutions don't work.....
>
>Anyone got a foolproof algorithm (language doesn't matter - just the logic)

A quick suggestion (VFP code):

SIGN(ABS(a1 - a2) - 180)

-1 = counter-clockwise
1 = clockwise
0 = either
Update: I just realized it doesn't work if angles in the 3rd and 4th quadrant. Sorry, Sat night here...