Abstract Histograms
We design an abstract “Histo1d” and “Histo2d” class, where the “real” histograms inherit from. The parent provides the interfaces “Fill”, “Reset”, and so on.
Remember that our code will be able to deal with other histogram classes which did not exist at the time when our code was compiled (as long as they inherit from “Histo1d” or “Histo2d”).
Phenix users beware: This here is the predecessor of the PhHistogramFactory; many things have changed (no Hbook, for example) .