Limited Rotation for Head/Body movement

I have a head and body, where I want the body (transform.rotation) to align slowly with the head (Quaternion.Euler(0, angleY, 0)), but if the head turns too far, the body will follow immediately at a 90 degree limit. My code works with one direction, but not with the commented out direction. I know that Quaternion.Angle is only returning a positive angle, but I am unsure how to determine if the angle difference is negative. I still have limited knowledge on how to use Quaternions, so am I going about this the wrong way?

Code (CSharp):

1.        
2.         if (Quaternion.Angle(transform.rotation, Quaternion.Euler(0, angleY, 0)) > 90)
3.         {
4.             transform.rotation = Quaternion.Euler(0f, angleY - 90, 0f);
5.         }
6.         //else if (Quaternion.Angle(transform.rotation, Quaternion.Euler(0, angleY, 0)) < 90)
7.         //{
8.         //    transform.rotation = Quaternion.Euler(0f, angleY + 90, 0f);
9.         //}
10.         else
11.         {
12.             transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.Euler(0, angleY, 0), Time.deltaTime * speed);
13.         }

 

I found my answer. I can get a signed angle from Vector3.

Code (CSharp):

1. if (Quaternion.Angle(transform.rotation, Quaternion.Euler(0, angleY, 0)) > 90f)
2.         {
3.             float angle = Vector3.SignedAngle(transform.forward, Quaternion.Euler(0, angleY, 0)*Vector3.forward, Vector3.up);
4.             if(angle > 0)
5.             {
6.                 transform.rotation = Quaternion.Euler(0f, angleY - 90f, 0f);
7.             }
8.             else
9.             {
10.                 transform.rotation = Quaternion.Euler(0f, angleY + 90f, 0f);
11.             }
12.         }
13.         else
14.         {
15.             transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.Euler(0, angleY, 0), Time.deltaTime * speed);
16.         }