Section concat_const_seq.
Variable A : Setoid.
Let eqa : forall a : A, Predicate A.
intro; apply Build_Predicate with (fun a' => a' =' a in _).
red in |- *; simpl in |- *.
intros; apply Trans with x; auto with algebra.
Defined.

Lemma concat_const_seq :
forall (n m : Nat) (a a' a'' : A),
a =' a' in _ ->
a' =' a'' in _ ->
const_seq n a ++ const_seq m a' =' const_seq (n + m) a'' in _.