Proof using.
intros t; elim t; simpl in |- *; auto.
intros b H b0 H0 H1.
apply unique_key_app; auto.
apply unique_key_map; auto.
apply H; apply distinct_leaves_l with (1 := H1); auto.
intros (a1, b1) (a2, b2); simpl in |- *; auto.
apply unique_key_map; auto.
apply H0; apply distinct_leaves_r with (1 := H1); auto.
intros (a1, b1) (a2, b2); simpl in |- *; auto.
intros a b1 c H2 H3.
case in_map_inv with (1 := H2); auto; case in_map_inv with (1 := H3); auto.
intros (a1, l1) (Ha1, Hl1) (a2, l2) (Ha2, Hl2).
apply (H1 (leaf a) b b0); auto.
injection Hl2; intros HH1 HH2; rewrite HH2.
apply inCompute_inb with (1 := Ha2).
injection Hl1; intros HH1 HH2; rewrite HH2.
apply inCompute_inb with (1 := Ha1).
Qed.

(* Specifications: *)
(* If a tree has distinct leaves its code is prefix *)
Theorem btree_unique_prefix :
forall t : btree, distinct_leaves t -> unique_prefix (compute_code t).