proposition: Lemma sf_ssub F s : sf_closed F -> s \in F -> ssub s `<=` F.
proof: Proof. case: s. elim => [|p|s IHs t IHt|s IHs] [|] sfc_F inF //=; rewrite ?fsetU0 ?fsubUset ?fsub1 ?inF ?IHs ?IHt ?andbT //=; move: (sfc_F _ inF) => /=; try bcase. Qed.
imports: Relations mathcomp.ssreflect.ssreflect mathcomp(all_ssreflect) CompDecModal.libs(edone bcase fset base modular_hilbert sltype)