I have a problem where I have a polygonal curve that I am using to define a castle wall, there is a straight wall segment between the points and a castle tower at each point. what I think I want to do is find the angle (I guess in world co-ordinate) to the previous and next points. I have a door way that is cut out of the tower at the top of the wall, and I want to rotate the hole with a stamped value so that the hole is then pointed at the next (or previous) point and aligned with the wall so the doorway is aligned with the wall. Any suggestions on an expression to find the angle to the next point?

Why you don't use edge_dir !?
I think you can take Angle between next and previous point simply with edge_dir :?