proposition: Lemma rRegEX s t : prv (s ---> t) -> prv (fEX s ---> fEX t).
proof: Proof. move => H. rule axReg. exact: rGen. Qed.
imports: mathcomp.ssreflect.ssreflect mathcomp(all_ssreflect) CompDecModal.libs(edone bcase fset base modular_hilbert) CompDecModal.CTL(CTL_def hilbert)