The file `AbsFunction.hh`, from `GeoModel/GeoModelCore/GeoGenericFunctions`---which has been adapted from the [CLHEP](proj-clhep.web.cern.ch) package---, defines the interface to `GENFUNCTIONS` and must be included. In addition, if specific functions such as trig functions, higher transcendental functions or physics-specific functions are required, header files for these function-objects should be included from the same area.
The file `AbsFunction.hh`, from `GeoModel/GeoModelCore/GeoGenericFunctions`---which has been adapted from the [CLHEP](https://proj-clhep.web.cern.ch) package---, defines the interface to `GENFUNCTIONS` and must be included. In addition, if specific functions such as trig functions, higher transcendental functions or physics-specific functions are required, header files for these function-objects should be included from the same area.
The headers `GeoXF.h` and `GeoSerialTransformer.h` are needed for the classes `TRANSFUNCTION` and `GeoSerialTransformer`, respectively.
