Class describing a 2D cartesian coordinate system
(x, y coordinates)
@ingroup GenVector
| Double32_t | fX | |
| Double32_t | fY |

Set internal data based on 2 Scalar numbers
get internal data into 2 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 =======