I mainly overhauled HS (hide_structs). The main idea is to make all structural prfs applicable to all types, including all struct-induced ones. This includes not only _shape_VxA_, _dim_A_, and co but I also made _zero_A_ directly available for all types.
That way, we no longer obtain "unexpected" definitions for sel and zero when defining a struct.
The "downside" of this approach is that all new struct-definitions now require explicit definitions of these in the same way as user-defined types do.
This further strengthens the desire to support element-type polymorphism!