During week 7 I continued my work on transformation equations for rotation. One PR #12960 which obtains transformation equations from rotation matrix was merged. I have prepared also method for composition of transformation equation but I didn’t push them. I need to still think how to arrange the whole structure. My mentor suggest that we can just use transformation equations instead of rotation matrix, because it’s just general concept. After that we could modify constructor in CoordSys3D class and put them transformation equation instead of rotation matrix. I think it’s good idea but it introduce lots of work with adaption of method which deals with rotation of coordinate system.

The second topic which I got involved was unevaluated expression. In PR #12987 we have added class Dot and Cross. In this Pr we also add possibility to call ‘dot’ and ‘cross’ products independently from Vector class.

For directional_derivative there are still some work. We need to create class which will be callable if no scalar or vector is put and otherwise not. The simplest solution is to create two separate class but I’m trying to omit this because I think that it’s not intuitive for user.