proposition: Lemma set_iterF_sub i : iterF i \subset iterF i.+1.
proof: Proof. by elim: i => [| i IHi]; rewrite /= ?sub0set ?F_mono. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)