proposition: Lemma set_meet_unique S x : lbound S x -> (forall y, lbound S y -> y <= x) -> x = set_meet S.
proof: Proof. move=> xlb xglb; apply/le_anti; rewrite set_meet_ge_lb //=. exact/xglb/set_meet_lb. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype choice order) mathcomp(ssrnat bigop classical_sets)