func angdiff a b .
   r = (b - a) mod 360
   if r < -180
      r += 360
   elif r >= 180
      r -= 360
   .
   return r
.
proc pd a b . .
   print b & " " & a & " -> " & angdiff a b
.
pd 20 45
pd -45 45
pd -85 90
pd -95 90
pd -45 125
pd -45 145
pd 29.4803 -88.6381
pd -78.3251 -159.036
pd -70099.74233810938 29840.67437876723
pd -165313.6666297357 33693.9894517456
pd 1174.8380510598456 -154146.66490124757
pd 60175.77306795546 42213.07192354373