class HRaNode: public TObject

_HADES_CLASS_DESCRIPTION

HRaTree, HRaNode, HRaIndexNode

 HRaTree stands for "Hades Random Access Tree". This class implements
random access to the objects in any category using a tree; the only condition
is that the data objects in the category inherit from HLocatedDataObject, so
the random access implemented by the HRaTree corresponds to the indexes
in the data objects rather than the natural indexing in the category.

 As said, the HRaTree is a tree of HRaNode objects. The lower level nodes
are HRaIndexNode and store pointers to the actual data objects being accesed
with the HRaTree.