proposition: Theorem add_frequency_list_not_in : forall m a b n, a <> b -> In (a, n) m -> In (a, n) (add_frequency_list b m).
proof: Proof. intros m; elim m; clear m; simpl in |- *; auto. intros (a1, l1) l H a0 b n H0 [H1| H1]; case (A_eq_dec b a1); simpl in |- *; auto. intros H2; case H0; injection H1; auto. intros; apply trans_equal with (2 := sym_equal H2); auto. Qed.
imports: Coq(List Sorting.Permutation) Huffman(AuxLib UniqueKey)