proposition: Lemma compat_P_aux : forall (P : elt -> Prop) (Pdec : forall x : elt, {P x} + {~ P x}), compat_P E.eq P -> compat_bool E.eq (fdec Pdec).
proof: Proof. unfold compat_P, compat_bool, Proper, respectful, fdec; intros. generalize (E.eq_sym H0); case (Pdec x); case (Pdec y); firstorder. Qed.
imports: FSetInterface