"functionXal" is a class of functionals (typically
integrals) typically of functionX-class functions. Since the functionX functions typically also depend on tuning
parameters, objects of this class ("functionXal") are functions
of these tuning parameters.
"function", from data part.
Class "OptionalFunction", by class "function".
Class "PossibleMethod", by class "function".functionX-class;
psiFunc, and
psi_func-class which has several functionXal slots.