#!/usr/bin/env newlisp
(define (bearing- bearing heading) (sub (mod (add (mod (sub bearing heading) 360.0) 540.0) 360.0) 180.0))

(bearing- 20 45)
(bearing- -45 45)
(bearing- -85 90)
(bearing- -95 90)
(bearing- -45 125)
(bearing- -45 145)
(bearing- 29.4803 -88.6381)
(bearing- -78.3251 -159.036)
(bearing- -70099.74233810938 29840.67437876723)
(bearing- -165313.6666297357 33693.9894517456)
(bearing- 1174.8380510598456 -154146.66490124757)
(bearing- 60175.77306795546 42213.07192354373))