proposition: Lemma wf_tl : forall l cl, wf (l :: cl) -> wf cl.
proof: Proof. unfold wf. intros. destruct H as (l1 & l2 & EQ); subst. destruct l1. simpl in EQ. destruct l2; try discriminate. inv EQ. exists nil,l2. reflexivity. inv EQ. exists l1,l2. reflexivity. Qed.
imports: ZArith List Bool Lia Morphisms Cdcl.Syntax Cdcl.Lib Cdcl.Lit Cdcl.Clause