proposition: Lemma eqVfproper A B : A `<=` B -> A = B \/ A `<` B.
proof: Proof. by rewrite subEfproper => /predU1P. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)