intros;induction l1;simpl.
reflexivity.
unfold ClausetoPropF in IHl1 at 1;rewrite IHl1.
apply orb_assoc.
Qed.

(* Specifications: *)
Lemma CNF_add_clause_valid : forall v l ll, TrueQ v (CNFtoPropF (AddClause l ll)) =
TrueQ v (ClausetoPropF l) || TrueQ v (CNFtoPropF ll).