fact: Definition is_successor_of (x y: T):= (x < y)%O /\ forall z, (x < z)%O -> ~~ (z < y)%O.
imports: mathcomp(all_ssreflect zify) mathcomp(fintype) Coq(Logic.Eqdep_dec) Coq(Wellfounded.Inclusion Wf_nat Inverse_Image)