Mapping Sets and Hypersets into Numbers
Giovanna D’Agostino, Eugenio Giovanni Omodeo, Alberto Policriti, Alexandru Ioan Tomescu · Fundamenta Informaticae · 2015
We introduce and prove the basic properties of encodings that generalize to non-well-founded hereditarily finite sets the bijection defined by Ackermann in 1937 between hereditarily finite sets and natural numbers.