RosettaCodeData/Task/Angle-difference-between-two-bearings/Common-Lisp/angle-difference-between-two-bearings.lisp

(defun angle-difference (b1 b2)
	   (let ((diff (mod (- b2 b1) 360)))
	     (if (< diff -180)
		 (incf diff 360)
		 (if (> diff 180)
		     (decf diff 360)
		     diff))))