# Angle difference between two bearings

proc getdiff(b1, b2) is
  r := (b2 - b1) symmod 360.0;
  if r >= 180.0 then r -:= 360.0 fi;
  if r < -180.0 then r +:= 360.0 fi;
  return r
end;

proc printrow(b1, b2) is
  printf("%14.6f    %14.6f    %14.6f\n", b1, b2, getdiff(b1, b2))
end;

scope
  print("Input in -180 to +180 range");
  print("     Bearing 1         Bearing 2        Difference");
  printrow(20.0, 45.0);
  printrow(-45.0, 45.0);
  printrow(-85.0, 90.0);
  printrow(-95.0, 90.0);
  printrow(-45.0, 125.0);
  printrow(-45.0, 145.0);
  printrow(-45.0, 125.0);
  printrow(-45.0, 145.0);
  printrow(29.4803, -88.6381);
  printrow(-78.3251, -159.036);
  print();
  print("Input in wider range");
  print("     Bearing 1         Bearing 2        Difference");
  printrow(-70099.74233810938, 29840.67437876723);
  printrow(-165313.6666297357, 33693.9894517456);
  printrow(1174.8380510598456, -154146.66490124757);
  printrow(60175.77306795546, 42213.07192354373)
epocs