proposition: Lemma wf_merge_clause : forall c1 c2, wf c1 -> wf c2 -> wf (Elim.merge_clause c1 c2).
proof: Proof. intros. unfold wf in *. destruct H as (l1 & l2 & EQ). destruct H0 as (l1' & l2' & EQ'). subst. exists (l1 ++ l1') ,(l2 ++ l2'). unfold Elim.merge_clause. rewrite! split_clause_wf. rewrite! map_app. rewrite <- !app_assoc. reflexivity. Qed.
imports: ZArith List Bool Lia Morphisms Cdcl.Syntax Cdcl.Lib Cdcl.Lit Cdcl.Clause