Class describing a 3D cartesian coordinate system
      (x, y, z coordinates)
      @ingroup GenVector

      Set internal data based on an array of 3 Scalar numbers
      get internal data into an array of 3 Scalar numbers
      Set internal data based on 3 Scalar numbers
      get internal data into 3 Scalar numbers
       set all values using cartesian coordinates
============= Compatibility section ================== The following make this coordinate system look enough like a CLHEP vector that an assignment member template can work with either
{ return X();}====== Set member functions for coordinates in other systems =======