Proof using.
intros a1 l1; elim l1; simpl in |- *; auto.
intros b; case b; simpl in |- *; auto.
intros l H t; case t; simpl in |- *; auto.
intros a H0 H1; rewrite all_pbleaves_pbleaf; simpl in |- *; auto.
rewrite all_pbleaves_pbleaf; intros p H0 H1.
apply ulist_app; simpl in |- *; auto.
intros a H2 [H3| H3]; auto; (case H0; rewrite H3); auto.
apply all_pbleaves_inpb; auto.
intros p p0 H0 H1; apply ulist_app; auto.
apply ulist_app_inv_l with (1 := H1); auto.
apply H.
Contradict H0; auto.
apply ulist_app_inv_r with (1 := H1); auto.
intros a H2 H3; case all_pbleaves_pbadd with (1 := H3).
intros H4; Contradict H0; rewrite <- H4; apply all_pbleaves_inpb;
simpl in |- *; auto with datatypes.
intros H4; apply ulist_app_inv with (1 := H1) (a := a); auto.
intros l H t; case t; simpl in |- *; auto.
intros a H0 H1; rewrite all_pbleaves_pbleaf; simpl in |- *; auto.
rewrite all_pbleaves_pbleaf; intros p H0 H1.
apply ulist_app; simpl in |- *; auto.
intros a [H3| H3] H2; auto; (case H0; rewrite H3); auto.
apply all_pbleaves_inpb; auto.
intros p p0 H0 H1; apply ulist_app; auto.
apply H.
Contradict H0; auto.
apply ulist_app_inv_l with (1 := H1); auto.
apply ulist_app_inv_r with (1 := H1); auto.
intros a H2 H3; case all_pbleaves_pbadd with (1 := H2).
intros H4; Contradict H0; rewrite <- H4; apply all_pbleaves_inpb;
simpl in |- *; auto with datatypes.
intros H4; apply ulist_app_inv with (1 := H1) (a := a); auto.
Qed.

(* Specifications: *)
(* Adding a new leaf to a tree with distinct leaves creates a tree with distinct leaves *)
Theorem distinct_pbleaves_pbadd_prop2 :
forall a1 l1 l,
~ inpb (pbleaf a1) l ->
distinct_pbleaves l -> distinct_pbleaves (pbadd a1 l l1).