proposition: Lemma unfold_concat: forall s0 s1, s0 ++ s1 = match_concat concat s0 s1.
proof: Proof. intros. rewrite unfold_stream with (concat s0 s1). simpl. destruct (match_concat concat s0 s1) eqn:T; reflexivity. Qed.
imports: Paco.paco Program.Tactics RelationClasses Morphisms