Finding the angle between two bearings is often confusing.[1]



Task

Find the angle which is the result of the subtraction b2 - b1, where b1 and b2 are the bearings.


Input bearings are expressed in the range   -180   to   +180   degrees.

The  result  is also expressed in the range   -180   to   +180   degrees.



Compute the angle for the following pairs:

 20 degrees (b1) and 45 degrees (b2)
 -45 and 45
 -85 and 90
 -95 and 90
 -45 and 125
 -45 and 145
 29.4803 and -88.6381
 -78.3251 and -159.036


Optional extra
 
Allow the input bearings to be any (finite) value.



Test cases

 -70099.74233810938 and 29840.67437876723
 -165313.6666297357 and 33693.9894517456
 1174.8380510598456 and -154146.66490124757
 60175.77306795546 and 42213.07192354373


class AngleBearings {
   function : Main(args : String[]) ~ Nil {
      "Input in -180 to +180 range"->PrintLine();
      GetDifference(20.0, 45.0)->PrintLine();
      GetDifference(-45.0, 45.0)->PrintLine();
      GetDifference(-85.0, 90.0)->PrintLine();
      GetDifference(-95.0, 90.0)->PrintLine();
      GetDifference(-45.0, 125.0)->PrintLine();
      GetDifference(-45.0, 145.0)->PrintLine();
      GetDifference(-45.0, 125.0)->PrintLine();
      GetDifference(-45.0, 145.0)->PrintLine();
      GetDifference(29.4803, -88.6381)->PrintLine();
      GetDifference(-78.3251, -159.036)->PrintLine();
 
      "Input in wider range"->PrintLine();
      GetDifference(-70099.74233810938, 29840.67437876723)->PrintLine();
      GetDifference(-165313.6666297357, 33693.9894517456)->PrintLine();
      GetDifference(1174.8380510598456, -154146.66490124757)->PrintLine();
      GetDifference(60175.77306795546, 42213.07192354373)->PrintLine();
   }
 
   function : native : GetDifference(b1 : Float, b2 : Float) ~ Float {
      r := Float->Mod(b2 - b1, 360.0);
      if (r < -180.0) {
         r += 360.0;
      };
 
      if (r >= 180.0) {
         r -= 360.0;
      };
 
      return r;
   }
}