-lemma tls_eq_repl (A) (n): eq_stream_repl A (λt1,t2. ⫰*[n] t1 ≗ ⫰*[n] t2).
-#A #n elim n -n //
-#n #IH * #n1 #t1 * #n2 #t2 #H elim (eq_stream_inv_seq … H) /2 width=7 by/
+lemma stream_tls_succ (A) (n) (t):
+ (⫰⫰*[n]t) = ⫰*{A}[↑n]t.
+#A #n #t
+@(niter_succ … (stream_tl …))