proposition: Lemma xchoose_rel (T : choiceType) (e : rel T) : (forall x, exists y, e x y) -> exists f, forall x, e x (f x).
proof: Proof. move => serial_e. exists (fun x => xchoose (serial_e x)) => x. exact: xchooseP. Qed.
imports: mathcomp.ssreflect.ssreflect mathcomp(all_ssreflect) CompDecModal.libs(edone bcase fset base modular_hilbert) CompDecModal.CTL(CTL_def hilbert)