proposition: Lemma carac_incl: forall (A:Type)(P Q:A -> Prop)(Pdec: dec P)(Qdec: dec Q), incl P Q -> carac Pdec <= carac Qdec.
proof: Proof. intros; intro x; unfold carac. case (Pdec x); case (Qdec x); intuition. absurd (Q x); intuition. Qed.
imports: ALEA(Utheory) ALEA(Sets)