proposition: Lemma is_lub_Rbar_unique (E : R -> Prop) (l : Rbar) : is_lub_Rbar E l -> Lub_Rbar E = l.
proof: Proof. move => Hl ; rewrite /Lub_Rbar ; case: ex_lub_Rbar => l' /= Hl'. apply Rbar_le_antisym. by apply Hl', Hl. by apply Hl, Hl'. Qed.
imports: Coq(Reals ssreflect) Rbar Rcomplements Markov