>>>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)
>>
>>Possibility one : move1 = the difference between oldPos and newPos gives a distance and a direction
>>
>>The other possibility (move2) is to take the opposite direction, where the distance is 360 - abs(move1)
>>
>>Take the move with the minimum absolute value
>
>May be being thick but I don't see how that works. Can you demonstrate with these examples:
>
>Old New
>
>350 2 (Should be clockwise)
>10 190 (Doesn't matter)
>20 190 (Clockwise)
>10 350 (Anti-clockwise)
>90 70 (Anti-clockwise)
>5 190 (Anti-clockwise)
>2 350 (Anti-clockwise)
>
>I don't care about the length of the arc - just in which direction to move.

Our definition of direction differs. To me 2 to 350 is clockwise

	? GetRotation(20, 335)
	? GetRotation(335, 20)
	? GetRotation(350, 2)
	? GetRotation(20, 190)
	? GetRotation(2, 350)

function GetRotation( from, to)
	
	from = mod(from, 360)
	to = mod(to, 360)
	
	local move1, move2, move, direction
	
	move1 = to - from
	move2 = (360 - abs(move1)) * (-sign(move1 ))
	
	move = iif(abs(move1) < abs(move2), move1, move2)
	direction = iif(sign(move) <=0, 'clockwise', 'counter-clockwise')
	
	? from, '->', to, ' degrees', abs(move), direction 
endfunc
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