Ah, I think I understand the unit_vector variable type now! Key to my revelation was realizing that I think it’s intended as a intermediate/helper variable and that you need to transform it to get at quantities of interest. For example, if interested in an angle on a circle, you’d define a unit_vector[2] angle_helper parameter and then compute the angle as a transformed variable: real angle = atan2(angle_helper[1],angle_helper[2]);
Full example is here.