fact: Definition restrict {A} (p: A -> bool) (r: A -> A -> bool):= fun x y => [&& (p x), (p y) & r x y].
imports: mathcomp(all_ssreflect zify) mathcomp(fintype) Coq(Logic.Eqdep_dec) Coq(Wellfounded.Inclusion Wf_nat Inverse_Image)