proposition: Lemma eqEfproper A B : (A == B) = (A `<=` B) && ~~ (A `<` B).
proof: Proof. by rewrite negb_and negbK andb_orr andbN eqEfsubset. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)