Class describing a polar coordinate system based on r, theta and phi
       Phi is restricted to be in the range [-PI,PI)
       @ingroup GenVector
| Double32_t | fPhi | |
| Double32_t | fR | |
| Double32_t | fTheta | 

      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
 setters (only for data members)
       set the r coordinate value keeping theta and phi constant
       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();}============= Specializations for improved speed ================== (none) ====== Set member functions for coordinates in other systems =======