proposition: Lemma fproperIl A B : ~~ (A `<=` B) -> A `&` B `<` A.
proof: Proof. by move=> nsBA; rewrite fproperE fsubsetIl fsubsetI negb_and nsBA orbT. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)