When following procedures linked to angles, you are sometimes required to ensure the angle falls within a 360 degree range of values. (Adding multiples of 360 degrees to an angle does not normally affect Trig function results but reduced accuracy is possible when applying Trig Functions to huge angles)
The following functions convert out_of_range values into equivilent within_range equivilents.

Private Function Range_360(angle As Double) As Double
 ' Force angle into the range 0 to 360
 angle = angle Mod 360
 If angle < 0 Then angle += 360
 Return angle
End Function
'
Private Function Range_180(angle As Double) As Double
 ' Force angle into the range -180 to +180
 angle = angle Mod 360
 If angle < 0 Then angle += 360
 If angle >= 180 Then angle -= 360
 Return angle
End Function
'
Private Function Range_2Pi(angle As Double) As Double
 ' Force angle into the range 0 to (2 * Pi))
 angle = angle Mod (2 * Math.PI)
 If angle < 0 Then angle += (2 * Math.PI)
 Return angle
End Function
'
Private Function Range_Pi(angle As Double) As Double
 ' Force angle into the range -Pi to + Pi
 angle = angle Mod (2 * Math.PI)
 If angle < 0 Then angle += (2 * Math.PI)
 If angle >= Math.PI Then angle -= 2 * Math.PI
 Return angle
End Function
  

The function below is a "generic" version of the above suitable for any valid range maximum and range minimum. However, care should be taken when using it for these reasons

• Angle ranges are normally 0_to_360, -180_to_180, 0_to_2*Pi or -Pi_to+Pi. The above functions handle each of these scenarios. Ranges between other limits are very unusual
• I would normally expect max_x to be exactly 180 degrees (2*Pi radians) more than min_x
• The function will fail or produce unexpected results unless max_x is significantly more than min_x

Private Function Range(x As Double, min_x As Double, max_x As Double) As Double
 Dim mmr As Double = max_x - min_x
 x = x Mod mmr
 If x < min_x Then x += mmr
 If x >= max_x Then x -= mmr
 Return x
End Function
  

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